CA1335604C

CA1335604C - Liquid-crystal display unit for electronic directory

Info

Publication number: CA1335604C
Application number: CA000604165A
Authority: CA
Inventors: Ronald Arden Wray; Richard A. Davidson; Paul Szymanski; Dennis W. Mowers; William R. Davis; Richard P. Greenthal
Original assignee: Sentex Systems Inc
Current assignee: Sentex Systems Inc
Priority date: 1988-07-07
Filing date: 1989-06-28
Publication date: 1995-05-16
Anticipated expiration: 2012-05-16
Also published as: US5027111A; US5252955A

Abstract

A liquid-crystal display, preferably twenty-five lines of eighty characters each, is mounted in a case. The temperature of the display medium is maintained within operating limits for the display -- notwithstanding ambient temperature and humidity variations over generally normal ranges for at least the temperate zones, and even if the display unit is placed to receive direct sunlight. The unit works outdoors as well as in buildings that lack temperature control. This is accomplished preferably by circulating air from outside the case through a space between the display face and an unperforated protective polycarbonate window. Intake and exhaust plena are long and narrow enough to deter manual access to the display and thus vandalism; however, the plena are straight and sufficiently free of obstruction that the fan can be a very small, low-power, quiet unit. A temperature sensor controls the fan, and also the contrast-adjusting voltage of the display -- base on data in a digital-memory "look up" table. A heater is preferably provided, also temperature-controlled. The plena face downward so that the unit is not sensitive to rain, and the entire unit can be flush-mounted in a wall without disrupting system cooling. Visible glare arising in reflection at the window is reduced by an antireflection coating on the window.

Description

3 l. FIELD OF THE INVENTION

This invention relates generally to practical display 6 units for electronic directories and like electronic 7 tabulations for public viewing; and more particularly to a 8 display unit for an electronically controlled directory 9 that employs a liquid-crystal display.

12 2. PRIOR ART

14 Directories are commonly posted in the public lobbies of business buildings, apartment houses, multiple-building 16 condominimum complexes, and other multiple-occupant 17 facilities. In secured facilities, the entries in such 18 directories often include room or suite numbers, or other 19 numbers for use with an adjacent telephone or intercom in contacting individual occupants to gain admission.
21 In a few large facilities, recently, hand-lettered or 22 movable-letter directories have given way to electronic 23 systems that are much easier to revise. Such systems 24 eliminate tedious manual reshuffling of placards or letters to keep entries in alphabetical order and to accommodate 26 subdivision or consolidation of occupant suites.
27 Although they are an enormous improvement over manual 28 directories, the electronic systems have suffered from a~

1 3356~4 1 major limitation in their use of cathode-ray-tube (CRT) 2 display units. Such video display units, in the forms 3 currently encountered in commercial practice, have several 4 well-known drawbacks.
The drawbacks of CRT displays include image 6 instability, poor resolution and (particularly in bright 7 light) poor contrast. Instability of the image, ranging 8 from minor flicker to vertical roll, can make reading the 9 information on the screen difficult.
Poor resolution severely limits the number of entries 11 that can be displayed simultaneously on a screen of 12 moderate size. This strategy sometimes leads to very large 13 screens that visually dominate a lobby.
14 Some system designers attempt to avoid this drawback by programming the units in operating modes that call upon 16 a visitor to "page through" different screens to find a 17 particular occupant. The "page through" mode itself is in 18 principle entirely acceptable, but when the number of 19 entries on a screen is unduly small -- so that a typical visitor must search through several screens even for a 21 relatively small directory -- the typical visitor 22 justifiably becomes annoyed. That is what happens with a 23 CRT display, because of its limitations.
24 Alternative methods for locating an occupant without paging are either more complicated or more expensive, or 26 both. For example, some systems provide a large 27 alphanumeric keypad and require the user to spell the first 28 few letters of the occupant's name. This increases the 1 system cost and also reduces convenience, particularly for 2 a user who is unsure how to spell the name.
3 In general all these drawbacks also detract from 4 efforts by facility management to establish an elegant or prestigious style in a lobby or outdoor entry area. Poor 6 contrast is considered among the worst offenders in this 7 regard.
8 Sometimes, in the interest of offsetting poor 9 contrast, directory system designers introduce the use of colors in the video display. Often, however, this strategy 11 is counterproductive, because the CRT or video colors 12 inject an incongruously gaudy element into a fine decor.
13 CRT displays are particularly troublesome in brightly 14 lit environments such as outdoors and in lobbies surrounded by large windows that admit brilliant sunlight. In these 16 circumstances, contrast can be so inadequate that the 17 displays are almost completely unreadable.
18 Moreover, CRT displays are relatively expensive. In 19 large formats they are too deep (front to back) for straightforward mounting in a wall -- and so require 21 provision of a free-standing or recessed support structure 22 enclosure two or three feet deep. Because of their 23 evacuated-chamber construction, they are also relatively 24 fragile and inordinately subject to vandalism.
Other types of display are known for use with 26 electronic information processors, but heretofore not with 27 electronic directories or other large electronic 28 tabulations for public viewing. Such other types include 1 the light-emitting diode (LED) and the liquid-crystal 2 display (LCD).
3 Most LEDs require relatively bulky apparatus for each 4 character to be displayed. Furthermore LEDs are quite dim, and in the few very-small-screen outdoor applications where 6 they have been used (such as some automatic-teller 7 machines) they are extremely hard to read -- even when 8 elaborately shaded. A larger LED array such as required 9 for a directory would be prohibitively difficult to shade effectively and would be inordinately expensive.
11 Under ideal conditions, liquid-crystal displays are 12 capable of excellent contrast and resolution, are plainly 13 readable even in the brightest light, and are readily 14 backlighted for nighttime use. Their use would also result in a far less expensive and much more compact product 16 package. LCDs would accordingly be excellent candidates 17 for directories and the like, but we are not aware of any 18 prior suggestion for such use; and they do have important 19 limitations.
An LCD has a display medium -- the liquid-crystal 21 fluid itself -- and a structure which contains the fluid.
22 In at least some commercial LCDs this structure typically 23 includes two planar pieces of material with the medium 24 sandwiched between them. At least the piece on the viewing side of the sandwich, which in this document we will call 26 the LCD "face," ordinarily is transparent glass or plastic.
27 Electrodes are formed on the opposed interior surfaces 28 of this sandwich. These electrodes too are ordinarily 1 transparent on at least the face side. One electrode 2 material is intrinsic tin oxide.
3 Both the fluid and the glass are very sensitive to 4 temperature. (It may be recalled that the early applications of liquid-crystal displays were as novelty 6 items, particularly including thermometers.) 7 If the temperature of the glass rises beyond certain 8 relatively narrow limits, the display develops dark spots, 9 or the entire display may actually turn dark. As we understand it, this darkening is due to an expansion of the 11 cell gap within the glass. The black characters or other 12 symbols then fail to stand out well against the darkening 13 background.
14 On the other hand, if the temperature falls too much, the changing of characters begins to be very slow, an 16 effect which is said to be related to increasing viscosity 17 of the medium. As temperature decreases further the 18 display blushes a different color (e. g., pink) -- this 19 time because of the cell gap's contraction -- and again becomes unreadable.
21 Directory applications would call for use of the 22 larger graphic LCDs, and also for a type of medium known as 23 " supertwist" fluid. This kind of fluid provides far 24 superior contrast and hence significantly better readability. The large LCDs, however, and especially those 26 using supertwist fluid, are particularly sensitive to 27 temperature.
28 Presumably for these reasons LCDs heretofore have 1 been used primarily in applications involving small formats 2 or intrinsic temperature control, or both. Thus LCDs are 3 employed extensively for wristwatches -- since they can 4 make good use of LCDs that are smaller and nonsupertwist, and therefore less temperature-sensitive. LCD wristwatches 6 also take advantage of the wearer's limited temperature 7 tolerance, and heat conduction to and from the wearer's 8 body, to limit the severity of temperatures to which the 9 display is exposed.
Even under such relatively protected conditions, 11 fading and blushing or wristwatch displays is well known to 12 athletes and workers whose activities reach the anticipated 13 design limits of the watches.
14 LCDs are also used for many usually indoor applications such as calculators and laptop computers.
16 Here too they are typically used in temperature-controlled 17 environments, or if they are found to malfunction can 18 generally be moved into such environments.
19 Operation of large LCDs would be subject to temperature problems in lobbies and other indoor entryways, 21 as well as outdoors, if the locations receive intense 22 sunlight. Temperature rise in such areas sometimes 23 outstrips the capabilities of a building air-conditioning 24 system, and can be severe enough to degrade the performance Of an LCD.
26 If the LCD were inside a case, and were protected from 27 vandals by an unbreakable window, as is desirable in our 28 application, the temperature problem would be aggravated 1 much further. This would be due to a "greenhouse" effect, 2 in which stagnant air between the window and the LCD
3 becomes extremely hot, much like the interior of a car left 4 shut on a hot day.
A related problem of LCD temperature sensitivity 6 involves a voltage that is applied to the display medium to 7 control the contrast of the characters relative to the 8 background screen. The necessary voltage for proper 9 contrast varies very strongly and nonlinearly with temperature.
11 Thus, as the temperature to which the LCD is exposed 12 changes (e. g., between day and night), the LCD contrast 13 would have to be constantly adjusted-to prevent its 14 characters from disappearing or becoming illegible. A very nonlinear relationship between the voltage and the 16 temperature renders the problem of automatic 17 contrast-control technique far from straightforward.
18 For whatever reason, LCDs have not been used in 19 sizable directory-type displays. We will return to more general discussion of electronic directories and the like.
21 Another problem arises in configuration of such 22 directories and the like, when outdoor or bright-lobby 23 applications are involved. That is the problem of 24 controlling reflections at glass or plastic surfaces of the display unit.
26 Such reflections of the viewing person -- and of 27 objects around and behind that person, become confused with 28 the displayed characters, making them very hard to read.

1 When sufficiently bright, these reflections actually 2 obscure the displayed characters.
3 As a verbal shorthand we shall refer to these 4 confusing and obscuring reflections collectively as "glare." Such glare can be controlled to a certain extent 6 by providing a matte finish on the screen itself, provided 7 that the electronic display screen (such as a CRT screen) 8 is directly exposed to the viewing person. Direct exposure 9 of the display screen is accordingly a conventional teaching of the prior art.
11 This conventional teaching, however, severely limits 12 the use of electronic directories since it makes them 13 susceptible to vandalism. Direct exposure of the display 14 screen makes it easy for a vandal to break the screen or damage the display unit.
16 Hence there is a conflict between the direct exposure 17 desired to control glare, and the interposition of an 18 intermediate protective window desired to control vandals.
19 This conflict is present with CRTs and LEDs -- but particularly acute with LCDs because of the very way they 21 work.
22 CRTs and LEDs inherently generate their own 23 illumination, but LCDs usually depend upon incident light 24 for their characters to be seen. Different portions of the fluid will either absorb or reflect incident light, and 26 thus form visible characters, depending on whether or not 27 the fluid is electrically excited.
28 This mechanism explains why LCD characters do not 1 3356~4 1 seem to fade in direct sunlight as do CRT and LED
2 characters. Light that is reflected at a glass or plastic 3 surface, however, is light not used to develop visible LCD
4 characters -- and, in fact, is light that creates reflections which compete with the already diminished LCD
6 characters.
7 Thus, again, even if there had been a suggestion of 8 LCD use in electronic directories, such a suggestion would 9 have been particularly likely to meet with immediate rejection in view of the relatively adverse glare-related 11 properties of LCDs.
12 Finally, even though the electronic directory systems 13 currently available are far more convenient in terms of 14 entering and deleting names than the movable-letter or placard directories, they still require local procedures 16 for entries or revisions -- either at the system itself or 17 through a computer close by. This arrangement is very 18 inconvenient for buildings that have off-site property 19 management, especially when tenant turnover is high and frequent directory changes required.
21 All of the above limitations have resulted in the 22 relatively limited use of currently available electronic 23 directories. As can now be seen, the prior art has failed 24 to provide an adequate display system for directories and the like, particularly for use out of doors and in lobbies 26 or other entryways subject to intense sunlight.

~ 33560~

3 Our invention is a display unit for an electronic 4 directory. It includes a case, and it also includes a liquid-crystal display (LCD) that is mounted within the 6 case.
7 Like all liquid-crystal displays, the LCD that is part 8 of our display unit has a display fluid, liquid or the like 9 which we will call the "display medium"; and a structure (described in an earlier section of this document) that 11 contains the fluid. As is well known, the operating 12 temperature of the display medium and structure -- and 13 therefore of the display in general -- has a distinctly 14 limited range. Even within this limited range, performance varies strongly with temperature.
16 Our display unit also includes some means for 17 maintaining the temperature of the liquid-crystal display 18 medium and structure between practical operating limits for 19 the display. For generality of expression in describing our invention, we shall refer to these means as the 21 "temperature- maintaining means."
22 These temperature-maintaining means are at least 23 partially mounted within the case. They maintain the 24 display-medium and display-structure temperature within its operating range notwithstanding ambient temperature and 26 humidity variations over generally normal ranges for at 27 least the temperate zones.
28 Furthermore the temperature-maintaining means 1 maintain the temperature within practical limits even if 2 the display unit is placed to receive direct sunlight when 3 the sun is out.
4 The foregoing may be a definition of our invention in its broadest or most general terms. For maximum enjoyment 6 of the benefits of our invention, however, we prefer to 7 incorporate certain additional features or characteristics 8 into devices made in accordance with the invention.
9 For example, we prefer that the temperature-maintaining means hold the temperature of the medium and 11 structure at least between positive 160 degrees and 12 negative 35 degrees Fahrenheit. We consider these limits 13 adequate to provide reasonably good,-reliable performance.
14 To provide even better and more reliable performance, however, we prefer that the temperature-maintaining means 16 hold the temperature of the medium and structure between 17 even tighter limits. It will be understood that there is a 18 continuum of improving performance and reliability with 19 progressively narrower operating limits, so that no absolute values can be stated; but through much careful 21 trial and error it is possible to select temperature limits 22 that are cost effective.
23 Accordingly we prefer that the temperature-maintaining 24 means hold the temperature of the medium at least between positive 120 degrees and negative 15 degrees Fahrenheit.
26 We prefer that the temperature-maintaining means do so in 27 direct sunlight with ambient temperature between 115 and 28 -40 degrees Fahrenheit.

1 In a preferred form of our invention, the 2 temperature-maintaining means include an external viewing 3 window mounted to the case and generally spaced away from 4 the LCD face, along the viewing direction. The viewing window thus defines an air-circulation region immediately 6 adjacent to the face. This window is preferably breakage 7 resistant and so provides an additional important 8 function: resistance to vandalism.
9 This preferred embodiment also has some means for defining intake and exhaust plena. Again for purposes of 11 generality in expression, we will call these means the 12 "plenum-defining means."
13 The plenum-defining means define an intake plenum 14 leading from the outside of the case to the air-circulation region, and a separate exhaust plenum leading from the 16 air-circulation region to the outside of the case. Each 17 plenum is long and narrow enough to substantially deter 18 manual access to the liquid-crystal display through the 19 plena.
The preferred embodiment under discussion also has at 21 least one fan disposed to circulate air from the intake 22 plenum through the air-circulation region to the exhaust 23 plenum. The intake and exhaust plenum terminations at the 24 outside of the case face downward, and preferably are in the bottom of the case itself.
26 In principle the viewing port can simply be left open 27 -- that is, with no viewing window at all -- to optimize 28 the air circulation for temperature control.

1 Alternatively the viewing window can be perforated, to 2 provide some air circulation through the window port as 3 well as behind it. Omitting the viewing window also has 4 the advantage that there is no glare-producing reflective surface spaced forward from the LCD.
6 Such systems are in fact within the scope of our 7 invention as most broadly defined above. They may be 8 preferable in some types of installations, particularly 9 where the risk of vandalism is minimal. That is so, for example, where the display unit is only exposed to 11 employees of the facility or to other prequalified 12 personnel.
13 For more general applications, however, even at the 14 cost of some benefit in temperature and glare control, we prefer to enhance security by including a viewing window 16 that is free of perforations. We have found that even with 17 such a window it is possible to achieve completely adequate 18 temperature control with very low cost, low power 19 consumption and low fan noise.
In particular we achieve these advantages by using a 21 fan that is free of air-flow obstructions such as guard 22 meshes or louvres, and by making each plenum at least very 23 generally straight and substantially free of air-flow 24 resista~ce elements such as guard meshes, louvres, or abrupt surface discontinuities of the plenum itself.
26 This geometry makes it possible to achieve the needed 27 air circulation using only a very quiet, low-power fan.
28 For best temperature control, we prefer to provide two 1 335b04 1 such fans, one associated respectively with each plenum.
2 We dispose each fan substantially adjacent to the LCD
3 face, substantially out of sight of viewers ex~m;n;~g the 4 LCD medium through the viewing window along typical viewing directions. It will be understood that the fan or fans 6 need not be operated at all times, but only when ambient 7 temperature and incident sunlight cause the temperature to 8 drift outside acceptable operating limits.
9 We prefer to include a temperature sensor for monitoring the temperature of the LCD medium. We also 11 prefer to include some means for controlling the fan in 12 response to the sensor. Again for generality, we shall 13 call these the "fan-controlling means."
14 We prefer to use the same sensor to adjust the LCD
contrast-control voltage too. The sensor controls that 16 voltage through a voltage-adjusting circuit that includes 17 an analog-to-digital ("A/D") temperature-conversion stage 18 and a digital electronic memory. This memory holds a 19 lookup table for establishing desirable contrast-control voltage values for various temperatures.
21 After some experimentation we have come to prefer this 22 system because the voltage requirement varies strongly with 23 temperature, particularly toward the extremes of the 24 temperature operating range, and is difficult to represent in closed form as by a formula. We prefer to include A/D
26 conversion of temperature because representing the 27 voltage-temperature relationship with an analog circuit is 28 relatively difficult and expensive.

1 Because that relationship is difficult to represent in 2 closed form as by a formula, we prefer to use a look-up 3 table. This approach has the added benefit of allowing us 4 to easily change the relationship to account for differences in display lots or even different displays we 6 might subsequently use.
7 We also prefer to provide a heater for raising the LCD
8 temperature, and to provide "heater-controlling means" for 9 operating the heater only when needed. The heater-controlling means are also responsive to 11 temperature.
12 As previously mentioned, visible glare can arise in 13 reflection at the solid viewing window. Nonreflecting 14 glass such as is used with picture frames fails to cure such glare, as the nonreflecting characteristic is attained 16 by using a matte finish; and only images immediately behind 17 the glass are clearly visible through such a finish.
18 It may be emphasized that the LCD face itself 19 typically carries such a matte finish, which does in fact minimize glare arising at the LCD face. The glare now 21 under discussion, however, arises not at the LCD face but 22 at the forward viewing window.
23 We have found that such glare can be effectively 24 controlled by vacuum-depositing an antireflection coating of the type used for eyeglasses. Resort to this solution 26 is far from obvious, since the equipment used for coating 27 eyewear is particularly configured for that purpose --28 particularly for simultaneous coating of a large number - I ; 1 3356~4 1 of small lenses, not our much larger viewing windows.
2 Once it is called for, however, the modification of 3 such equipment for coating viewing windows of the type 4 under discussion here is straightforward, for a person skilled in the art of mechanical devices.
6 The viewing window is preferably of unbreakable 7 plastic such as polycarbonate. The best materials for use 8 in forming a graded-index antireflection coating for the 9 window accordingly may differ from those used for eyeglasses.
11 In particular, we prefer to make the viewing window of n~r 12 the plastic available commercially under the trade namc 13 "Lexan." After some experimentation it has been found that 14 the antireflection coating may include three layers of material on both sides of the Lexan window, each layer 16 being a different material. In the alternative, with 17 better performance, five layers may be used on both sides 18 of the window.
19 The formulation for the three-layer and five-layer alternatives can be those commercially available from 21 Pacific Universal Corporation in Pasadena, California, 22 under the names "AR-narrow band" and "AR-broad band"
23 formulations, respectively, for polycarbonate. These names 24 would also identify similar composite coatings of other suppliers.
26 As mentioned earlier, prior to our invention, all 27 electronic directories required local programming, either 28 at the unit or through a computer close by, via a hardware ~ 1 335604 connectlon. Our electronlc dlrectory system can lnstead be programmed remotely from any locatlon vla telephone llne, uslng elther a modem and terminal or a tone-transmlttlng telephone by ltself. In the latter case, our electronlc dlrectory system provldes syntheslzed volce responses to CUpply status and progress lnformatlon to the programmer over the telephone.
Our system can also be programmed locally, uslng a very lnexpenslve handheld membrane-type alphanumerlc keypad that plugs lnto the system electronlcs dlrectly. Alternatlvely, the system, can also be programmed uslng a twelve-button keypad on the front panel of the system.
In accordance wlth a broad aspect of the lnventlon there ls provlded a vandallsm-reslstant and weather-reslstant dlsplay unlt for an outdoor-lnstalled electronlc dlrectory, comprlslng:
a substantlally vandallsm-reslstant and weather-reslstant case for outdoor lnstallatlon;
a llquld-crystal dlsplay, mounted wlthln the case, and havlng a dlsplay medlum and a structure for contalnlng the dlsplay medlum;
the llquid-crystal dlsplay structure comprlslng a face dlsposed ln front of the medlum, for dlsplaylng dlrectory lnformatlon outdoors ln the form of a dlrectory;
means, at leat partlally mounted wlthln the case, for protectlng the llquld-crystal dlsplay agalnst vandallsm and ralnwater and for malntalnlng the temperature of the llquld-crystal dlsplay medlum and structure between practlcal operatlng ,~

1 335~04 llmlts for the dlsplay, notwlthstandlng amblent temperature and humldlty varlatlons over generally normal ranges for at least the temperate zones, and even lf the dlsplay unlt ls placed to recelve dlrect sunllght when the sun ls out; the protectlng and temperature-malntalnlng means comprlslng:
an external vlewlng wlndow mounted to the case and generally spaced away from the llquld-crystal dlsplay structure face, along a vlewlng dlrectlon, to protect the llquld-crystal dlsplay and to deflne an alr-clrculatlon reglon lmmedlately ad~acent to the face;
means deflning an lntake plenum leadlng from the outslde of the case to the alr-clrculatlon reglon, and a separate exhaust plenum leadlng from the alr-clrculatlon reglon to the outslde of the case, each plenum belng long and narrow enough to substantlally deter manual access to the llquld-crystal dlsplay through the plena; and at least one fan dlsposed to clrculate outdoors amblent air from the lntake plenum through the alr-clrculatlon reglon to the exhaust plenum to reduce heatlng by the sun; and solld-state dlgltal electronlc clrcultry, electrlcally lnterconnected wlth the llquld-crystal display, for electronlcally storlng dlrectory lnformatlon and for controlllng the llquld-crystal dlsplay unlt to automatlcally exhlblt stored dlrectory lnformatlon ln the form of a dlrectory havlng multlple llstlngs ln an alphabetlcal or llke order or ln classlfled grouplngs.
All of the foregolng operatlonal prlnclples and 18a ~, advantages of the present lnventlon wlll be more fully appreclated upon conslderatlon of the followlng detalled descrlptlon, wlth reference to the appended drawlngs, of whlch:
BRIEF DR~L~~ ON OF THE DRAWINGS
Flg. 1 ls an exterlor perspectlve drawlng, taken from sllghtly above and to one slde, of a dlsplay unlt that ls a preferred embodlment of our lnventlon.
Flg. 2 ls an lnterlor perspectlve vlew, taken from below and drawn partlally broken away, of the Flg. 1 embodlment wlth lts front panel opened to show the lnterlor constructlon and arrangement.

18b .
1 Fig. 3 is a side elevation, partly in cross-section 2 and enlarged, showing the relationships of the viewing 3 window, the LCD face, and the temperature sensor.

4 Fig. 4 is a block diagram of the programming processing flow for the system and shows the different 6 programming devices that can be used along with the major 7 electronic components used to process their input.

8 Fig. 5 is a picture of our handheld programmer -- one 9 of the devices used to program the system at the system.

14 As seen in Figs. 1 and 2, the preferred embodiment of our display unit has a case 101 that includes a front panel 16 107. The case 101 also includes a rear wall 103, left and 17 right side pillars 104, 105, a ceiling 106, a floor 107, 18 and a rain gutter 201 (Fig. 2). We prefer to make the 19 front panel stainless steel and the case painted cold-rolled steel.
21 The front panel 102 is hinged to the right pillar 105, 22 and provided with a keyed lock 107 that engages a strike 23 groove 202 (Fig. 2) formed in the left pillar 104 to secure 24 the front panel firmly against the rear parts 103-106 of the case. Formed in the front panel 102 are a viewing port 26 lll, louvres 112 and an array of twelve small square access 27 holes 113, a small hole 114 and a larger hole 115.
28 The louvres 112 are provided for transmission of 1 sound from an audio speaker 203 (Fig. 2) that is mounted 2 behind the front panel 102. The square access holes 113 3 accommodate twelve pushbuttons of a standard telephone-type 4 pushbutton array 116. The small hole 114 allows for transmission of sound to a microphone 204 (Fig. 2) that is 6 mounted directly behind the hole. The larger hole 115 is 7 for installation of a post-office key lock. If this lock 8 is not used, a plug fills the hole.
9 Securely mounted to the rear surface of the front panel 102, behind the viewing port 111, is a polycarbonate 11 viewing window 117, which carries an antireflection 12 coating. Behind the window is an LCD 120, preferably eight 13 to twenty-five rows of twenty to eighty characters each.
14 As previously explained, the antireflection coating on the window 117 reduces "glare" (as defined above) 16 sufficiently that the LCD 120 can be read. This function 17 is particularly important when the LCD is facing away from 18 the incident sunlight.
19 When that is so, the person attempting to read the LCD
is facing into the sun, and is brightly illuminated. Under 21 these circumstances the reflected image of the person's own 22 face and surroundings, as seen in the window 117, can be 23 extremely bright and can almost totally obscure the LCD.
24 It is believed that the provision of an antireflection coating in our invention is particularly unobvious, for at 26 least three reasons. First, the very existence of the 27 glare problem is much less evident than the problem of 28 temperature control.

1 In our own development of the present invention, all 2 our concern and early tests were directed to verifying that 3 our apparatus would work even with direct sunlight 4 impinging upon and heating the LCD. Therefore prototypes were always tested with the LCD facing toward the sun. We 6 did not realize that we had inadvertently selected a mode 7 of test in which the problem of glare was m;n;m~l.
8 On one occasion, when we had not yet perfected the 9 temperature control aspects of our invention, we were asked about the possibility of installing an electronic directory 11 in a north-facing wall. We supposed that such an 12 installation would be uneventful, since direct heat loading 13 in the particular facility could be very low.
14 After positioning a prototype in the subject facility, however, we were quite amazed to discover that the LCD in 16 the prototype was virtually invisible because of glare.
17 Only then did we become aware of this glare problem.
18 There is a second reason that use of antireflection 19 coating is particularly unobvious. The LCD industry has settled upon the use of antireflecting surfaces -- i. e., a 21 matte finish -- on the LCD face.
22 This is the industry's solution to reduction of what 23 little glare is present in use of a laptop computer and the 24 like. Such a finish cannot be used on windows that are spaced forward from the LCD, as we found by actual attempts 26 -- but the common wisdom of the industry in this regard 27 tends to distract attention from alternatives.
28 Another seemingly fruitful avenue was use of a tinted 1 window. Only after a significant effort could we conclude 2 that such a technique was not effective. The tinted window 3 reduced light transmission to and from the LCD, making it 4 too dim to read. What we needed was an antiglare coating 5 that was substantially invisible.

6 It was not through the teaching of the LCD or 7 directory industry, but only by happening to think of a 8 recent personal incident involving a different field, that 9 we came upon the idea of antireflection coatings. More specifically, one of the present inventors had only 11 recently ordered a pair of eyeglasses, and recalled having 12 been offered an antireflection coating at a small added 13 price. He also recalled that this coating was described as 14 untinted and invisible, and he accordingly thought that it might not suffer from the problems of other coatings.
16 There is yet a third reason for characterizing 17 eyeglass-type antireflection coatings as unobvious in 18 connection with the present invention. In our preliminary 19 inquiries regarding the possibility applying such coatings to our windows, we were consistently informed that such 21 application would be prohibitively expensive.
22 The basis for this information was that standard 23 equipment had developed for coating large numbers of 24 eyeglass lenses at once. Further, use for eyeglasses appeared to be the primary segment of the antireflection-26 coating industry. Without extensive modification, such 27 equipment was (and it is) inappropriate for coating viewing 28 windows large enough for an LCD screen.

- 1 33560~

1 Business people who have such equipment were 2 understandably reluctant to invest in such modification on 3 behalf of a new product with unproven market performance.
4 Accordingly we were led to believe that antireflection coating of our windows would be uneconomic.
6 That belief persisted until, after considerable 7 effort, we found a relatively small operator for whom our 8 project represented a significant amount of business. That 9 firm was accordingly willing to undertake the needed modifications.
11 It is possible that with future refinements of 12 fluorescent backlighting in LCDs it may become possible to 13 make the LCD itself so bright as to be clearly visible even 14 in the presence of glare at the viewing window. For the present, however, the provision of substantially invisible 16 antireflection coatings is an important advance.
17 Six metal extenders 205, spaced along the top and 18 bottom edges of the viewing port 111, stand the LCD 120 off 19 from the rear surface of the front panel 102, defining an air space between the viewing window 117 and the LCD 120.
21 These six extenders are fix`ed behind the panel 102 by six 22 mounting studs.
23 The extenders 205 pass through holes in the top and 24 bottom brackets 121, 122 and in the viewing window 117; and secure the brackets and viewing window in place. From the 26 perspective of a user of the apparatus, the brackets 121, 27 122 hide the extenders from view, providing a finished look 28 to the assembly.

1 The brackets also contour the air-circulation region, 2 to provide for more-nearly laminar air flow. The brackets 3 do not extend along the side edges of this air space, which 4 is accordingly unobstructed at both sides.
A circulating fan 125 is mounted to each side pillar 6 104, 105, along the inward-facing surface of the pillar and 7 near the ceiling 106. These fans 125 are vertically 8 aligned with the LCD 120, roughly, and are aligned in the 9 front-to-back direction so that the front half of each fan 125 is roughly adjacent to the air space formed between the 11 window 117 and LCD 120.
12 Strictly speaking the fans 125 are visible from 13 outside the case 101 by a viewer looking through the window 14 117 at an acute angle to the front panel 102 and window 117. Ordinarily, however, the fans 125 are outside the 16 lines of view of a person standing in front of the device 17 and reading the LCD 120. Moreover, advantageously the fans 18 are of dark-colored material while the screen and the front 19 panel 102 are of light-colored material, so that the fans are quite inconspicuous -- particularly when operating.
21 Each side pillar 104, 105 is a rectangular vertical 22 tube open at the bottom 206, 207, as shown (Fig. 2), 23 apertured at 208, 209 near the top along the inward-facing 24 surface for passage of air through the corresponding fan 125, and unobstructed between the bottom opening 206, 207 26 and the fan aperture 208, 209. Each pillar thus serves 27 double duty as a very sturdy structural member of the case 28 101 and as an air-passage duct or plenum.

1 !Depending upon the direction of fan operation, air 2 enters either opening 206 or 207, and is exhausted through 3 the other. For installations where temperature or sun 4 loading is never very high, one or the other fan 125 can be omitted.
6 From the scale established by the standard telephone 7 pushbutton array 116 it can be readily seen that each 8 plenum is too narrow for passage of a person's arm, and 9 contains no apparatus that could be readily damaged by insertion of a bar or other tool from the bottom. Hence 11 the plena are reasonably vandal resistant.
12 Yet they are also straight and unobstructed, and 13 therefore offer a very minimum of resistance to air 14 circulation by the fans 125. Consequently, as mentioned earlier, the fans can be of a particularly low-power, quiet 16 type such as the 1.8-watt, 18-cubic-foot-per-minute model 17 TFDD6012 RXA commercially available from the Toyo 18 Corporation of Japan.
19 Because the openings 206, 207 located at the base of the pillars 104, 105 face downward, rain cannot enter the 21 case through them. Moreover, this arrangement allows the 22 case to be flush-mounted in a wall without disrupting air 23 intake and exhaust.
24 The LCD itself is preferably a Model EG 2402-AR
supertwist type made by Seiko Epson Corporation, or a Model 26 LM 674 XGNR supertwist type, made by Hitachi Corporation.
27 The choice of models depends on whether the number of 28 occupants to be listed on the screen at once can be 1 adequately presented on an eight-line, forty-character 2 screen or justifies use of a sixteen-line, eighty-character 3 screen, respectively.
4 The display can be operated from a microprocessor or even a personal computer or other microcomputer, in very 6 generally conventional fashion. We prefer, however, to use 7 novel electronics and software which we have developed.
8 These additional subsystems optimize the performance of the 9 display as part of a novel programmable electronic directory system, as will be described shortly.
11 Immediately behind the window 117, in the space 12 between the window and the LCD 120, is a thermistor element 13 123, disposed to receive substantially the same 14 radiant-heat loading from incident sunlight as does the LCD
120. This thermistor, perhaps best seen in Fig. 3, is 16 excited and monitored by portions of the electronic 17 circuitry 211 within the case 101, and the resulting 18 temperature information is used to control both the fans 19 and the LCD contrast voltage.
As also shown in Fig. 2, a small strip heater 212 is 21 advantageously mounted behind the LCD 120. This heater too 22 is temperature-controlled; however, it need not be made 23 responsive to the thermistor 123. The heater element 24 itself is self-regulating: its resistance increases with temperature, tending to reduce heat output. The heater can 26 be a twelve-volt d. c. model CDH 00310 commercially 27 available from Midwest Components, Inc. of Muskegon, 28 Michigan.

Approximate dimensions (in inches) of the apparatus are collected here:
case 101 height 19 width 15.3 depth 3.8 port 111 height 5.3 width 10.3 window 117 height 6.5 width 11 thickness0.1 plena 104, 105 width 0.9 (pillars) depth 2.9 Thus our invention encompasses several important innovations relating to provision of a high-resolution, high-contrast, essentially glare-free display for electronic directories and the like. It is particulary advantageous in outdoor installations, and in building entries or lobbies where temperature and brightness of illumination are not well controlled.
Our invention further encompasses important innovations in a programmable electronic directory system. These innovations will be described herebelow.
As mentioned earlier, prior to this invention, electronic directory systems had to be programmed at the directory ';

-unit itself or by a computer close by. Our invention allows for programming of the directory from a remote location over the telephone lines using a modem and terminal or by using a standard tone-transmitting telephone by itself. The system can also be programmed locally using a handheld programmer 201 (Fig. 4), the system's keypad 202, or via the system's RS-232 communications port 203. Thus, in addition to providing both remote and local programming capabilities in the same machine, the system is capable of managing a multiplicity of programming input devices.
Moreover, the system can be programmed while it is being used without the programmer or the user realizing the other party is using the machine. However the system is programmed, names are automatically alphabetized and put in their proper location on the directory.
Figure 4 gives an overview of the programming processing flow and shows the different programming devices that can be used along with the major electronic components used to process their input. Local programming is generally done using a handheld programmer 201 of our own design (pictured in Fig. 5) which plugs directly into the system's electronics 211 (Fig. 2) via a ribbon cable 271. The programmer is a membrane keypad that simply provides contact closure output for alphabetic characters 272, numerals and other phone-system characters 273, and standard computer-keyboard functions 274, as well as directory and access functions 275. As a result, it is extremely rugged, very thin, small sized, and very inexpensive.
As can be seen from the graphics on the keypad, it as .~

well as our system can do substantially more than provide for an electronic directory. In one of its forms, the system can be a complete access control system providing for both occupant and visitor access control, using card or code entry for occupants and telephone entry for visitors. In this system configuration, the electronic directory would normally be part of the telephone entry function for visitor access control. The microphone 204 tFig. 2) and the speaker 203 (Fig. 2~ are for communications between the visitor and the person being contacted in the building whose name is listed on the electronic directory. This system configuration is, however, only one form in which the electronic directory could be used and in no way is intended to limit the scope of our claims.
The systems 12-button keypad 113/116 (Fig. 1) and 202 (Fig. 4), which also provides simple contact closure output, can also be used to program the system locally. In this instance, 2-digit numbers are used to encode letters. While the keypad 113/116,202 is more cumbersome for alphanumeric programming, it is a useful back-up in case the user has misplaced the handheld programmer 201.
The contact closure outputs of the handheld programmer 201 and system keypad 113/116,202 go to separate PIAs (Parallel Interface Adapters) 204, 205 and then via a bus 206 to the systems microprocessor 210. We use a Motorola 6809 microprocessor and Motorola 6821 PIAs. The PIAs 204, 205 serve to expand the available ports on the microprocessor 210 and have hardware "interrupts" (each being a pin on the chip that is in a high or -1 335~0~ 74593-1 low state) that alert the microprocessor 210 that data is on the PIA 204 or 205 and ready to be retrieved. Once the microphone 210 has retrieved that data from a single keypress it loads it into RAM (random access memory) 211 and displays it on the LCD 220 (120 in Figs. lff.) as it does programming prompts and messages. When the data entry from one or more keypresses has been completed it is then loaded into an EEPROM (electrically erasable programmable read only memory) 212 where it will reside until erased. We use an EEPROM for permanent memory because of its nonvolatility - the ability to keep its memory contents without any external power.
The EEPROM 212 we use is a Samsung 2864.
The third method of local programming is via the systems RS-232 port 203 using any RS-232 compatible device (e q., a terminal 207). Since the baud rate on the systems RS-232 port 203 is selectable (300, 1200, 2400, and 4800), the port will accommodate a wide range of devices 207. The serial ASCII data that comes into the RS-232 connection 203 goes to a UART
(Universal Asynchronous Receiver Transmitter) 208, which converts the serial data to parallel data and also has a hardware interrupt to alert the microprocessor 210 that the UART 208 has data. We use Motorola 6850 UART. The microprocessor handles the data the same as it does from the handheld programmer 201 and keypad 202, except that it displays the data on the device 207 connected to the RS-232 port 203 (e , the terminals 207 video screen).
The RS-232 port 203 also provides a means of remote programming in that a modem 231 can be connected to the RS-232 port 203 and thus allow communications with the system over the ~.

-telephone lines 232 from a remote location having a modem and terminal 233. Our system also has an onboard 300-baud modem chip (National 74HC943) 234 which eliminates the need for an outboard modem 231. An outboard modem 231 would be used only if a faster than 300-baud data transmission rate was desired. A "dumb"
terminal 207, 233 as opposed to a personal computer (PC~ can be used in either case since all the necessary intelligence resides in our system.
The serial ASCII data from the onboard modem 234 is sent to a UART 235 and then to the microprocessor 210. Data entries and system prompts are sent back to the modem 234 -- which then transmits them over the telephone line 236 to the modem and terminal 233 at the remote location where they are displayed on the terminals video screen.
A standard tone telephone 241 can also be used to program the system from a remote location. The DTMF (Dual Tone Multi Frequency) tones are received by a tone decoder chip (Mitel 8870) 242 in the systems electronics, which chip 242 decodes the frequencies by comparing them to a crystal oscillating at 3.579545 MHZ. The decoder chip 242 represents the decoded frequency in digital form, which is then sent through a PIA 243 to the microprocessor 210. The decoder chip 242 has a hardware interrupt, as does the PIA 243 for notification that data are ready for transmission. The microprocessor 210 processes the data as before except that instead of data and prompts being displayed on a screen, a voice chip (SSI-263) 244 generates synthesized voice responses and prompts 245 which are sent back over the previously mentioned telephone line 236 to the phone 241 and human programmer at the remote location.
The ability in the same electronic directory unit to be programmed via modem 234, 233 or by tone telephone 241, using just one telephone line 236 for the system, is not straightforward and is another novel aspect of our invention. As far as we are aware, all other systems, with both means of programming (not other electronic dlrectory systems which have neither capability) require two telephone lines, one for modem programming and the other for tone programming (e a., electronic banking systems).
The difficulty is that a means of sorting the incoming signal types from a common input source is needed. The source in this case is the unknown type of telephone call being answered.
We accomplish this by using an active hybrid circuit 246. The hybrid is an analog three-port circuit design having an input port 247, 247', an output 248, 248', and an input/output port 249 that enables the concurrent testing for either an incoming modem signal or a DTMF signal. The modem 234 transmitters section and voice chips 244 outputs are fed to the input port 247 and both the modem 234 receiver section and the DTMF receivers 242 inputs are connected to the hybrids 246 output port 248, 248'. The telephone-line 236 interface feeds signals both into and out of the active hybrids 246 input/output port 249.
When the system is called, it senses the ring signal on the line 236 and integrates these occurrences over a period of time to avoid falsely answering on noise pulses. The system then answers by seizing the line 236 and, after a 2.2 second delay, ~, ;
.-J

answers in English speech 245, saying, "Hello. n It then presents the modem 234 answering tone and "listens" concurrently for either an originate tone from a possible modem or originating station 233 or a DTMF tone from a possible phone 241. If an originate tone from a modem 233 is detected, the unit will ignore subsequent DTMF
tones. Conversely, if a DTMF tone is detected, the Infinity unit turns off its modem 234 answering tone, ignores any subsequent modem frequencies, and obeys only the incoming DTMF commands.
Another feature of the active hybrid 246 is the cancellation of leakage between the input port (transmitter output) 247, 247' and the output port (receiver input~ 248, 248'.
This is accomplished by the mathematics inherent in the design.
When the sidetone balance (the relative impedance of the system vs. the phone line 236) is adjusted properly, a close impedance match to the telephone is achieved and a high degree of output-to-input leakage suppression results. This condition makes it possible for multiplexing both the modem 234 and the DTMF receiver 242 on the same telephone line 236, since the modems 234 transmitter cannot overpower the sensitive DTMF receivers 242 input stage.
Finally, as mentioned earlier, one of the forms of our electronic directory system is as part of an access control system. When used in this configuration, the system has a buffer memory (part of RAM 211) capable of automatically storing the last several thousand transactions. Transactions include entries made using cards or codes, entries granted by telephone, as well as alarm conditions and the like. If the transaction buffer is =;;3 filled, the oldest transaction is deleted when a new transaction is entered. The information recorded for each transaction includes the time, date, type of transaction, entry point, card or code used, attached name, and action taken (e.q., access granted or denied).
Our system allows these data to be retrieved when the system is in the programming mode, either locally 201-208 or remotely 231-249, with the data displayed on the systems LCD 220, a printer (not shown), or a terminal 207, 233, depending on the programming mode as discussed earlier. The chip (part of RAM 211) we use for the transaction buffer memory is an RCA 6264 eight-thousand byte RAM or a RCA 62256 thirty-two thousand byte RAM.
The size depends on the maximum number of transactions wished to be retained.
We have also created a software program on floppy disk that allows the data in the transaction buffer to be sorted after it is retrieved. Sorting can be by date and time, source and type of transaction, code used, name, and action taken. Thus, a user can focus in more narrowly on the specific transactions he wishes to review.
The program also allows the programmed information stored in the systems EEPROM memory 212 (e q., names on the directory, codes, telephone numbers, etc.) to be downloaded to a floppy disk. Thus, a back-up disk file of the systems memory can be maintained. This is a particulary attractive feature with directory units having the capacity for a large number of names, where loss of the systems memory (e a., due to lightning strike) ,~

_ 1 335604 would necessitate reprogramming many names. With this floppy disk program, the names on the back-up disk file can simply be uploaded to the affected system once it is back in commission.
This floppy disk program can be used in any IBM-compatible PCs with DOS 2.0 or higher. The PC can be connected directly to the system via RS-232 connection 203 or it can communicate with the system via modem 231, 234 since the floppy disk program includes the terminal emulation and communications software necessary for a PC to be able to communicate via modem 231, 234.
It will be understood that the foregoing disclosure is intended to be merely exemplary, and not to limit the scope of the invention -- which is to be determined by reference to the appended claims.

r~
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Claims

1. A vandalism-resistant and weather-resistant display unit for an outdoor-installed electronic directory, comprising:
a substantially vandalism-resistant and weather-resistant case for outdoor installation;
a liquid-crystal display, mounted within the case, and having a display medium and a structure for containing the display medium;
the liquid-crystal display structure comprising a face disposed in front of the medium, for displaying directory information outdoors in the form of a directory;
means, at least partially mounted within the case, for protecting the liquid-crystal display against vandalism and rainwater and for maintaining the temperature of the liquid-crystal display medium and structure between practical operating limits for the display, notwithstanding ambient temperature and humidity variations over generally normal ranges for at least the temperate zones, and even if the display unit is placed to receive direct sunlight when the sun is out; the protecting and temperature-maintaining means comprising:
an external viewing window mounted to the case and generally spaced away from the liquid-crystal display structure face, along a viewing direction, to protect the liquid-crystal display and to define an air-circulation region immediately adjacent to the face;
means defining an intake plenum leading from the outside of the case to the air-circulation region, and a separate exhaust plenum leading from the air-circulation region to the outside of the case, each plenum being long and narrow enough to substantially deter manual access to the liquid-crystal display through the plena; and at least one fan disposed to circulate outdoors ambient air from the intake plenum through the air-circulation region to the exhaust plenum to reduce heating by the sun; and solid-state digital electronic circuitry, electrically interconnected with the liquid-crystal display, for electronically storing directory information and for controlling the liquid-crystal display unit to automatically exhibit stored directory information in the form of a directory having multiple listings in an alphabetical or like order or in classified groupings.

2. The display unit of claim 1, wherein:
the temperature-maintaining means hold the temperature of the medium and structure at least between positive 160 degrees and negative 35 degrees Fahrenheit.

3. The display unit of claim 1, wherein the temperature-maintaining means hold the temperature of the medium and structure at least between positive 120 degrees and negative 15 degrees Fahrenheit, in direct sunlight with ambient temperature between positive 115 and negative 40 degrees Fahrenheit.

4. The display unit of claim 1, wherein:

the intake and exhaust plenum terminations at the outside of the case face downward.

5. The display unit of claim 1, wherein:
the intake and exhaust plenum terminations at the outside of the case are in a bottom of the case; and the viewing window is of unperforated material.

6. The display unit of claim 1, for use in a facility that has a wall; and wherein:
the intake and exhaust plenum terminations at the outside of the case are in a bottom of the case; and the display unit is mounted with its viewing window generally flush with such facility wall.

7. The display unit of claim 1, wherein:
the fan is free of air-flow obstructions such as guard meshes or louvres;
each plenum is at least very generally straight and substantially free of air-flow resistance elements such as guard meshes, louvres, or abrupt plenum-surface discontinuities; and the fan is disposed substantially adjacent to the liquid-crystal display face.

8. The display unit of claim 7, wherein:
the fan is substantially out of sight of viewers examining the liquid-crystal display medium through the viewing window along typical viewing directions.

9. The display unit of claim 8 further comprising:
a temperature sensor for monitoring the temperature of the liquid-crystal display medium and structure; and means, responsive to the sensor, for controlling the fan.

10. The display unit of claim 9, further comprising:
means for automatically adjusting voltage to control contrast of the liquid-crystal display; and wherein the voltage adjusting means are also responsive to the sensor.

11. The display unit of claim 10, wherein:
the voltage adjusting means comprise analog-to-digital conversion means and digital electronic memory means; and the digital electronic memory means define a lookup table for establishing desirable contrast-control voltage values for various temperatures.

12. The display unit of claim 11 further comprising:
a heater for raising the temperature of the liquid-crystal display; and means, also responsive to temperature, for controlling the heater.

13. The display unit of claim 10, further comprising:

a heater for raising the temperature of the liquid-crystal display; and means, also responsive to temperature, for controlling the heater.

14. The display unit of claim 5, wherein:
the fan is free of air-flow obstructions such as guard meshes or louvres;
each plenum is at least very generally straight and substantially free of air-flow resistance elements such as guard meshes, louvres, or abrupt plenum-surface discontinuities; and the fan is disposed substantially adjacent to the liquid-crystal display structure face.

15. The display unit of claim 14 wherein:
the fan is substantially out of sight of viewers examining the liquid-crystal display medium through the viewing window along typical viewing directions.

16. The display unit of claim 1, further comprising:
substantially nonattenuating means mounted to the case, for reducing visible glare arising in reflection at the window.

17. The display unit of claim 5, further comprising:
substantially nonattenuating means, mounted to the case, for reducing visible glare arising in reflection at the window.

18. The display unit of claim 13, further comprising:
substantially nonattenuating means mounted to the case, for reducing visible glare arising in reflection at the window.

19. The display unit of claim 14, further comprising:
substantially nonattenuating means, mounted to the case, for reducing visible glare arising in reflection at the window.

20. The display unit of claim 15, further comprising:
substantially nonattenuating means, mounted to the case, for reducing visible glare arising in reflection at the window.

21. The display unit of claim 16, wherein:
the glare-reducing means comprise an antireflection coating on the viewing window.

22. The display unit of claim 20, wherein:
the glare-reducing means comprise an antireflection coating on the viewing window.

23. The display unit of claim 20, for use in a facility having a multiplicity of occupants; and wherein:
the liquid-crystal display has at least eight lines of at least twenty characters each, and serves as a directory to display a multiplicity of occupant names and respectively related alphanumeric information;
the viewing window is substantially taller than the liquid-crystal display structure face, and is disposed so that information displayed near top and bottom edges of the liquid-crystal display structure face is visible to viewers of greatly differing heights and at varying distances from the viewing window; and the display unit further comprises means for automatically controlling the display of said multiplicity of names and information, including automatically alphabetizing said names.

24. The display unit of claim 20 wherein:
the viewing window is at least one inch taller than the liquid-crystal display structure face, and is disposed so that a top edge of the viewing window is very roughly a half inch above the top edge of the liquid-crystal display structure face.

25. The display unit of claim 22, wherein:
the viewing window is at least one inch taller than the liquid-crystal display structure face, and is disposed so that a top edge of the viewing window is very roughly a half inch above the top edge of the liquid-crystal display structure face.

26. A vandalism-resistant and weather-resistant display unit for an outdoor-installed electronic directory, comprising:
a substantially vandalism-resistant and weather-resistant case for outdoor installation, said case including a front wall, side-wall structure, and a bottom wall;
a liquid-crystal display, mounted within the case, and having a display medium and a structure for containing the display medium;
the liquid-crystal display structure comprising a face disposed in front of the medium, for displaying directory information outdoors in the form of a directory;
means, at least partially mounted within the case, for protecting the liquid-crystal display against vandalism and rainwater and for maintaining the temperature of the liquid-crystal display medium and structure between practical operating limits for the display, notwithstanding ambient temperature and humidity variations over generally normal ranges for at least the temperature zones, and even if the display unit is placed to receive direct sunlight when the sun is out; the protecting and temperature-maintaining means comprising:
an external window mounted to the case in the front wall and generally spaced away from the liquid-crystal display structure face, along a viewing direction, to protect the liquid-crystal display and to define an air-circulation region immediately adjacent to the face;
means for establishing ambient air circulation at the liquid-crystal display, said circulation-establishing means comprising:
(1) ventilation-plenum means for conducting air between the outside of the case and the air-circulation region, said ventilation-plenum means being integrated into said side-wall structure, and including at least one vertical panel facing toward the liquid-crystal display; the ventilation-plenum means being long and narrow enough to substantially deter manual access to the liquid-crystal display through the ventilation-plenum means, (2) orifice means, defined in said panel, for conducting air between the air-circulation region and the ventilation-plenum means, and (3) at least one fan or blower, disposed at an opening in said panel to circulate outdoors ambient air therethrough, and through the ventilation-plenum means and the air-circulation region, and to return such air to the outside of the case, to reduce heating by the sun; and solid-state digital electronic circuitry, electrically interconnected with the liquid-crystal display, for electronically storing directory information and for controlling the liquid-crystal display unit to automatically exhibit stored directory information in the form of a directory having multiple listings in an alphabetical order or in classified groupings.

27. The display unit of claim 26, further comprising:
aperture means, defined in the bottom wall and facing downward, for communicating between the circulation-establishing means and the outside of the case.

28. The display unit of claim 26, wherein the circulation-establishing means further comprises:
generally continuous brackets disposed substantially along opposed edges of the liquid-crystal display and extended generally between said display and the front wall, and cooperating with the window and the liquid-crystal display structure face to form a well-defined channel for air flow immediately adjacent to the face of the display.

29. The display unit of claim 28, wherein:
the height of said orifice means above the bottom wall being very generally between the bracket heights; and the brackets tend to constrain air introduced by the circulation-establishing means to flow within the air-circulation region and across the face of said display.

30. The display unit of claim 26, further comprising:
means, on the window, for reducing visible glare arising in reflection at the window.

31. The display unit of claim 30, wherein:
the glare-reducing means comprise an antireflection coating on the window.

32. A vandalism-resistant and weather-resistant display unit for an outdoor-installed electronic directory, comprising:
a substantially vandalism-resistant and weather-resistant case for outdoor installation, said case including a front wall, side-wall structure, and a bottom wall;
a liquid-crystal display, mounted within the case, and having a display medium and a structure for containing the display medium;
the liquid-crystal display structure comprising a face disposed in front of the medium, for displaying directory information outdoors in the form of a directory;
means, at least partially mounted within the case, for protecting the liquid-crystal display against vandalism and rainwater and for tending to limit the temperature of the liquid-crystal display medium and structure even if the display unit is placed to receive direct sunlight; said means comprising:
an external window mounted to the case in the front wall and generally spaced away from the liquid-crystal display structure face, along a viewing direction, to protect the liquid-crystal display and to define an air-circulation region immediately adjacent to the face;
means for establishing ambient air-circulation at the liquid-crystal display, said circulation-establishing means comprising:
(1) ventilation-plenum means for conducting air between the outside of the case and the air-circulation region, said ventilation-plenum means being integrated into said side-wall structure, and including at least one vertical panel facing toward the liquid-crystal display; the ventilation-plenum means being long and narrow enough to substantially deter manual access to the liquid-crystal display through the ventilation-plenum means;
(2) orifice means, defined in said panel, for conducting air between the air-circulation region and the ventilation-plenum means, and (3) at least one fan or blower, disposed at an opening in said panel to circulate outdoors ambient air therethrough, and through the ventilation-plenum means and the air-circulation region, and to return such air to the out-side of the case, to reduce heating by the sun; and solid-state digital electronic circuitry, electrically interconnected with the liquid-crystal display, for electronically storing directory information and for controlling the liquid-crystal display unit to automatically exhibit stored directory information.

33. The display unit of claim 32, further comprising:
aperture means, defined in the bottom wall and facing downward, for communicating between the circulation-establishing means and the outside of the case.

34, The display unit of claim 32, wherein the circulation-establishing means further comprise:

generally continuous brackets disposed substantially along the top and bottom edges of the liquid-crystal display and extended generally between said display and the front wall, guiding air flow in the air-circulation region in a generally horizontal transverse pattern across the front of said display.

35. The display unit of claim 34, wherein:
the height of said orifice means above the bottom wall being very generally between the bracket heights; and the brackets tend to constrain air introduced by the circulation-establishing means to flow within the air-circulation region and across the face of said display.

36. The display unit of claim 32, further comprising:
means, on the window, for reducing visible glare arising in reflection at the window.

37. The display unit of claim 36, wherein:
the glare-reducing means comprise an antireflection coating on the window.

38. A vandalism-resistant and weather-resistant display unit for an outdoor-installed electronic directory, comprising:
a substantially vandalism-resistant and weather-resistant case for outdoor installation, said case including a front wall, side-wall structure, and a bottom wall;
a liquid-crystal display, mounted within the case, and having a display medium and a structure for containing the display medium;
the liquid-crystal display structure comprising a face disposed in front of the medium, for displaying directory information outdoors in the form of a directory;
means, at least partially mounted within the case, for protecting the liquid-crystal display against vandalism and rainwater and for maintaining the temperature of the liquid-crystal display medium and structure between practical operating limits for the display, notwithstanding ambient temperature and humidity variations over generally normal ranges for at least the temperature zones, and even if the display unit is placed to receive direct sunlight when the sun is out; the protecting and temperature-maintaining means comprising:
an external window mounted to the case in the front wall and generally spaced away from the liquid-crystal display structure face, along a viewing direction, to protect the liquid-crystal display and to define an air-circulation region immediately adjacent to the face;
means for establishing ambient air-circulation at the liquid-crystal display, said circulation-establishing means comprising:
(1) ventilation-plenum intake means for conducting air from the outside of the case to the air-circulation region, said ventilation-plenum intake means being long enough to substantially deter manual access to the liquid-crystal display through the ventilation-plenum means;

(2) intake orifice means, located in the bottom of the case for allowing the entry of ambient air into the ventilation plenum means and the air-circulation region, and separate exhaust orifice means, also located in the bottom of the case, to allow for the exit of said air from the case; both the intake and exhaust orifice means being small enough to substantially deter manual access through the intake and exhaust orifice means;
(3) at least one fan or blower, disposed at the exhaust orifice means, to return outdoors ambient air, after intake through the ventilation-plenum intake intake and passage through the air-circulation region, to the outside of the case, to reduce heating by the sun, and (4) generally continuous brackets disposed substantially along the top and bottom edges of the liquid-crystal display and extended generally between said display and the front wall, guiding air flow in the air-circulation region in a generally horizontal transverse pattern across the front of said display;
and solid-state digital electronic circuitry, electrically interconnected with the liquid-crystal display for electronically storing directory information and for controlling the liquid-crystal display unit to automatically exhibit stored directory information in the form of a directory having multiple listing in an alphabetical order or in classified groupings

39. The display unit of claim 38, wherein the height of said orifice means above the bottom wall being very generally between the bracket heights; and the brackets tend to constrain air introduced by the circulation-establishing means to flow within the air-circulation region and across the face of said display.

40. A vandalism-resistant and weather-resistant display unit for an outdoor-installed electronic directory, comprising:
a substantially vandalism-resistant and weather-resistant case for outdoor installation, said case including a front wall, side-wall structure, and a bottom wall;
a liquid-crystal display, mounted within the case, and having a display medium and a structure for containing the display medium;
the liquid-crystal display structure comprising a face disposed in front of the medium, for displaying directory information outdoors in the form of a directory;
means, at least partially mounted within the case, for protecting the liquid-crystal display against vandalism and rainwater and for tending to limit the temperature of the liquid-crystal display medium and structure even if the display unit is placed to receive direct sunlight; said means comprising:
an external window mounted to the case in the front wall and generally spaced away from the liquid-crystal display structure face, along a viewing direction, to protect the liquid-crystal display and to define an air-circulation region immediately adjacent to the face;
means defining an intake plenum leading from the outside of the case to the air-circulation region, said plenum being long and narrow enough to substantially deter manual access to the liquid-crystal display through the plenum;
a first fan or blower disposed in association with the intake plenum, for directing outdoors ambient air therethrough to the air-circulation region;
means defining a pathway, including an orifice defined in the case, for conducting air from the air-circulation region to the outside of the case; and a second fan or blower disposed in association with the orifice, for expelling air from the case to ambient; and solid-state digital electronic circuitry, electrically interconnected with the liquid-crystal display, for electronically storing directory information and for controlling the liquid-crystal display unit to automatically exhibit stored directory information.

41. The display unit of claim 40, wherein:
the orifice is defined in the bottom wall and facing downward.

42. The display unit of claim 40, further comprising:
generally continuous brackets disposed substantially along opposed edges of the liquid-crystal display and extended generally between said display and the front wall, and cooperating with the window and the liquid-crystal display structure face to form a well-defined channel for air flow immediately adjacent to the face of the display.

43. The display unit of claim 40, further comprising:
means, on the window, for reducing visible glare arising in reflection at the window.

44. The display unit of claim 43, wherein:
the glare-reducing means comprise an antireflection coating on the window.

45. A vandalism-resistant and weather-resistant display unit for an outdoor-installed electronic directory, comprising:
a substantially vandalism-resistant and weather-resistant case for outdoor installation, said case including a front wall, side-wall structure, and a bottom wall;
a liquid-crystal display, mounted within the case, and having a display medium and a structure for containing the display medium;
the liquid-crystal display structure comprising a face disposed in front of the medium, for displaying directory information outdoors in the form of a directory;
means, at least partially mounted within the case, for protecting the liquid-crystal display against vandalism and rainwater and for tending to limit the temperature of the liquid-crystal display medium and structure even if the display unit is placed to receive direct sunlight; said means comprising:
an external window mounted to the case in the front wall and generally spaced away from the liquid-crystal display structure face, along a viewing direction, to protect the liquid-crystal display and to define an air-circulation region immediately adjacent to the face,;
means defining a pathway, including an orifice defined in the case, for conducting air from the outside of the case to the air-circulation region; and a first fan or blower, disposed in association with the orifice, for directing outdoors ambient air therethrough to the air-circulation region;
means defining all exhaust plenum leading from the air-circulation region to the outside of the case, said plenum being long and narrow enough to substantially deter manual access to the liquid-crystal display through the plenum;
a second fan or blower disposed in association with the exhaust plenum, for expelling air from the case through the exhaust plenum to ambient; and solid-state digital electronic circuitry, electrically interconnected with the liquid-crystal display, for electronically storing directory information and for controlling the liquid-crystal display unit to automatically exhibit stored directory information.

46. The display unit of claim 45, wherein:
the orifice is defined in the bottom wall and facing downward.

47. The display unit of claim 45, further comprising:
generally continuous brackets disposed substantially along opposed edges of the liquid-crystal display and extended generally between said display and the front wall, and cooperating with the window and the liquid-crystal display structure face to form a well-defined channel for air flow immediately adjacent to the face of the display.

48. The display unit of claim 45, further comprising:
means, on the window, for reducing visible glare arising in reflection at the window.

49. The display unit of claim 48, wherein:
the glare-reducing means comprise an antireflection coating on the window.

50. A vandalism-resistant and weather-resistant display unit for an outdoor-installed electronic directory, comprising:
a substantially vandalism-resistant and weather-resistant case for outdoor installation, said case including a front wall and a bottom wall;
a liquid-crystal display, mounted within the case, and having a display medium and a structure for containing the display medium;
the liquid-crystal display structure comprising a face disposed in front of the medium, for displaying directory information outdoors in the form of a directory;

means, at least partially mounted within the case, for protecting the liquid-crystal display against vandalism and rainwater and for tending to limit the temperature of the liquid-crystal display medium and structure between practical operating limits for the display, even if the display unit is placed to receive direct sunlight, the protecting and temperature-maintaining means comprising:
an external window mounted to the case in the front wall and spaced away from the liquid-crystal display structure face, along a viewing direction, to protect the liquid-crystal display and to define an air-circulation region immediately adjacent to the face;
generally continuous brackets disposed substantially along opposed edges of the liquid-crystal display and extended generally between said display and the front wall, and cooperating with the window and the liquid-crystal display structure face to form a well-defined channel for air flow immediately adjacent to the face of said display;
air-flow guide means, including at least two apertures defined in the case, for circulating air from the outside of the case through the well-defined channel and returning the air to the outside of the case;
air-flow impelling means, comprising at least two fan or blower units associated with the air-flow guide means, for establishing a pressure differential directly across the well-defined channel to propel air through the well-defined channel;
said guide means and in particular said two apertures being arranged and disposed to substantially deter manual access to the liquid-crystal display through the guide means; and solid-state digital electronic circuitry, electrically interconnected with the liquid-crystal display, for electronically storing directory information and for controlling the liquid-crystal display unit to automatically exhibit stored directory information.

51. The display unit of claim 50, wherein:
the liquid-crystal display structure face is substantially planar;
the window is substantially planar and substantially parallel to the liquid-crystal display structure face;
the channel formed by the face, window and brackets is substantially straight; and the air flow through the channel is at least very generally laminar.

52. The display unit of claim 50, wherein:
the brackets are disposed substantially along the top and bottom edges of the liquid-crystal display; and the air-flow follows a generally horizontal transverse pattern across the front of said display.

53. The display unit of claim 50, wherein:
both apertures are defined in the bottom wall of the case and face downward.

54. The display unit of claim 50, wherein:
the air-flow guide means comprise an air-flow plenum that is long and narrow enough to substantially deter manual access through the plenum to the liquid-crystal display, and that is disposed to carry air substantially directly between the outside of the case and said channel.

55. The display unit of claim 50, further comprising:
means, on the window, for reducing visible glare arising in reflection at the window.

56. The display unit of claim 55, wherein:
the glare-reducing means comprise an antireflection coating on the window.