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Publication numberUS3852718 A
Publication typeGrant
Publication dateDec 3, 1974
Filing dateOct 25, 1973
Priority dateOct 25, 1973
Publication numberUS 3852718 A, US 3852718A, US-A-3852718, US3852718 A, US3852718A
InventorsLyria K De
Original AssigneeDutton H, Schulein J, Schulein M
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Apparatus for interpreting numerically coded pulse groupings in a line
US 3852718 A
Abstract
An electrical supervisory signaling system employing a plurality of McCulloh-type pulse transmitters which are operable selectively to transmit over a line one or more like groups, or "rounds," of time-spaced, numerically coded pulses. Single-"round" and multiple-"round" transmissions are used to indicate different monitored conditions. Receiving these pulses in the system is an interpreter which, through examining the time spacings between successive pulses, both distinguishes the transmissions from the different transmitters, and indicates whether a transmission from a given transmitter contains one or more "rounds" of pulses.
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ited States Patent 1191 De Lyria Dec. 3, 1974 [54] APPARATUS FOR INTERPRETING 3,587,l12 6/197] Hill 340/286 NUMERICALLY CO SE 3,599,195 8/1971 Boyko 340/213 R GROUPINGS IN A LINE Primary Examiner-Donald J. Yusko [75] Inventor: Karl G. De Lyria, Vancouver, Attorney, Agent, or FirmKolisch, Hartwell,

wash Dickinson & Stuart [73] Assignees: Hayward H. Dutton; Joseph I Schulein; Margaret A. Schulein, all [57] ABSTRACT f Vancouver washpart mterest An electrical supervisory signaling system employing a to each plurality of McCulloh-type pulse transmitters which [22] Filed; O t, 25, 1973 are operable selectively to transmit over a line one or more like groups, or rounds," of time-spaced, numer- [21] Appl 409766 ically coded pulses. Single-round and multipleround" transmissions are usedtoindicate different 52 us. (:1 340/164 R, 340/293, 340/286 monitored conditions Receiving these Pulses in the 51 Int. Cl. G08b 25/00 System is an interpreter which, through examining the [58] Fi ld f S h 340/164 R 167 R 168 R time spacings between successive pulses, both distin- I 340/293 213 R guishes the transmissions from' the different transmitters, and indicates whether a transmission from a [56] References Cit d given transmitter contains one or more rounds of UNITED STATES PATENTS Pulses- I 3,399,350 8/1968 Lisle 340/164 R 6 Claims, 5 Drawing Figures MI :o 1:52 r- -1 26 I 52 84 64 90 70 I I mp5 /22 I Np r g-2 PA'AD I M zw 1 A i c/er b/r/ 32% I 4 I 4% I r/wu/r I I a D L 1 me I I Z8 I 5 j PULSF I I; 75 ye ma /:2 I I I I PFSZT 75 Z //5- I menu/f M I I I I can; W [Fa r/01v 1 I I Q 335, J 5 Call/V712 I My 1 I r/Ms'e Ma 50 7 i i 2 I F -K I 55735 I l //0 f umv 1 H58 l fl/flW/T 4 i 1 femur/ml? l I Mlfififfdl/P f I fg y an 1 l Arum/AA g I I 2 I /52 Mme me :72 l I /26 60 I L 6 1 L w 3 APPARATUS FOR INTERPRETING NUMERICALLY CODED PULSE GROUP-INGS IN LINE I BACKGROUND AND SUMMARY OF THE INVENTION This invention pertains to an electrical supervisory signaling system of the type employing aplurality of McCulloh-type pulse transmitters. More particularly, it relates to an interpreter usable in such a system for automatically and reliably sorting out and interpreting the various transmissions therein of the different transmitters employed in the system.

A typical McCulloh-type transmitter includes a notched rotary wheel which may be turned selectively by a motor, such as by an electric or a spring-wound motor. Thenotches and lands in the wheel, with the latter turning, alternately open and close an associated electrical switch, which action is used to generate electrical voltage pulses in a line, such as in a conventional telephone line.

The arrangement of notches and lands provided in such a wheel defines a numerical pulse code for a transmitter. A typical code includes a group, or round," of pulses divided into three sections, with each section containing one or more pulses. As an illustration, one code might be 2-3-1, resulting in a pulse group containing a first section including two timespaced pulses, a second section containing three timespaced pulses, and a third and final section containin a single pulse. 1

A transmitter of the type just generally described is often set up to operate in two different modes so as to be able to respond to two different monitored conditions. In one mode of operation, the transmitter transmits but a single roundfof pulses, and in the other mode transmits two or more rounds. To illustrate, a transmitter set up to monitor the condition of a fire sprinkler system might be arranged to transmit but. a single round if a non-fire-induced break occurs in the system, and more than one round in the eventof the system turnin on to handle a fire.

Further explaining what is conventional, within a coded round of pulses, it is usually intended that successive pulses within a section in the round be spaced apart by one'u'niform preselected time, and that successive sections in the round be spaced apart by another, longer preselected uniform time. Further, it is normally the case that successive rounds transmitted by a trans mitter are spaced apart longer than the spacings between successive sections within a round. All of this practice, of course, is to aid in distinguishing rounds, and in distinguishing pulse sections within a round. With McCulloh-type transmitters, individual pulses normallly last between about .25-1 .S-seconds, with the spaces between adjacent pulses in a section being the same width as thepulses. Further,'it is usually the case that the time spacing used between successive sections in a' round is about twice the spacing used between pulses in a section. The same two-to-one relationship normally typifies the length'of the space between sucthe transmitter which is capable of producing such a round operated so as to produce successive rounds, the time spacings therebetween wouldv typically be about l-second for the example just described.

One of the problems with transmitters of the type just outllined is that the pulse widths, and the different pulse spacings, associated with a transmitter are not uniform, even within the transmission of a single round of pulses. This is partly due to the mechanical tolerances permitted in the manufacture of a notched wheel in a transmitter, and also partly due to the fact that the wheel when turned may not be rotated at a constant speed. As a consequence, the electrical pulse waveform transmitted by such a transmitter is not entirely predictable, and can be difficult to interpret.

A. further problem is that transmitters of the type outlined have typically been used heretoforeiin systems wherein recording-type receivers, such as rolled paper tape recorders, have been used. What is recorded by such a recorder must be monitored by a person, and interpreted by him so, as to distinguish different codes that may be transmitted in a system. Such an arrangement introduces'considerable delay in obtaining desired information, and is quite prone to errors.

A general object of the present invention, therefore, is to provide novel means usable in a signaling system with transmitters of the type above outlined to receive and interpret transmissions therefrom in a manner avoiding the difficulties just mentioned.

More specifically, an object of the invention is to provide a novel electrical interpreter which is capable of ignoring. pulse width and pulse spacing irregularities in the transmission from such a transmitter, and which is further capable of accurately and reliably distinguishing the coded transmissions of different transmitters which may be used in a system.

Still another object of the invention is to provide such an interpreter which is capable of determining whether the transmission from a given transmitter includes, on the one hand, a single coded round of pulses, or on the other hand, more than one round of pulses.

According to a preferred embodiment of the invention, an interpreter is proposed which accomplishes the above-stated objectives through examining major differences in the time spacings between successive pulses transmitted over a line in a system, thus to determine the beginnings and endings of different rounds, as well as the beginnings and endings of different pulse sections in a round. Included in the interpreter, for each transmitter employed in the system with which the interpreter is used, is a programmed memory capable of responding to, but only to, the coded transmission of but one of the transmitters in the system.

The interpreter of the invention continuously, and without the need for human intervention, monitors the signal conditions in a line in a system, and essentially immediately reports on each transmission in the sys tem, with each such report specifically identifying which transmitter has operated, and what information it transmitted.

These and other objects and advantages attained by the invention will become more fully apparent as the description which follows is read in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS 4 FIG. 1 is a simplified diagram partially showing a sig naling system employing McCulloh transmitters and a receiving interpreter as contemplated by the present invention.

FIG. 2 is a block diagram illustrating details of the interpreter used inthe system of FIG. 1.

FIG. 3 is a block diagram illustrating, in greater detail, a portion of the interpreter of FIG. 2.

And, FIGS. 4 and S are similar graphs illustrating, along a time base, several different voltage waveforms which appear at different points in the interpreter of FIG. 2 during two different modes of operation of the interpreter.

DETAILED DESCRIPTION OF THE INVENTION 1. Explanation of Terminology Explaining briefly certain terminology which will be used in the description which follows, various components shown in the drawings operate in a response to a pair of voltage levels. More specifically, one of these levels corresponds to a certain positive voltage (typically about +5 volts) which will be referred to hereinaf ter as a 1 state. The other level corresponds essentially to ground, and will be called hereinafter a 0 state. A terminal or a conductor having one of these voltage levels on it will be referred to as being in, or as having on it, either a l or a 0 state.

2. Description of .the Logic Gates Used Among the components illustrated in the drawings which respond to the two voltage levels just mentioned are certain logic gates. More specifically, four different types of gates, all conventional in construction, are employed. These are referred to as AND, NAND, OR and NOR gates.

An AND gate functions as follows: with a 0 state on any input of the gate, the output thereof is held in a 0 state; with all inputs in 1 states, the output is placed also in a I state.

In a NAND gate: with a 0 state on any input, the output is held in a I state; with all inputs in 1 states, the output is placed in a Ostate.

In an OR gate: if any input is in a I state, the output of the gate is held also in a I state; if all inputs are in 0 states, then the output is also in a 0 state.

Finally, a NOR gate functions whereby: if any input is in a I state, the output is held in a 0 state; if all inputs are placed in 0 states, then the output is placed in a I state.

The operations of other components shown in the drawings which respond to these two voltage levels will be explained as such components are encountered in the description which follows.

3. The Signaling System Generally Turning now to the drawings, and referring first to FIG. 1, indicated generally at is what is referred to herein as a conductive signaling system including-remotely located transmitting and receiving portionsl2, 14, respectively, which are represented in FIG. 1 as being separated by a dashed line 16. System 10 herein is used for reporting fire status and sprinkler system status information with respect to a plurality of facilities, such as storage warehouses, that are located remote from the receiving portion of the system. The term fire status" is used herein to mean whether or not a fire exists; and the term sprinkler system status" is intended to mean whether or not a sprinkler system is operative.

Included in the transmitting portion of system 10 are a plurality of conventional, electric-motor-driven McCulloh transmitters, or signalers, such as the two shown in block form at 18, 20. Each such transmitter is employed with respect to a different facility herein, and each is set up to operate in either of two different modes of operation. In one of these operating modes, a transmitter produces a single round, or group, of coded pulses-- this being done to indicate that the sprinkler system in the associated facility has become inoperative. In the other operating mode, a transmitter transmits, one after another, a plurality of rounds of pulses to indicate that a fire exists at the associated facility. The way in which the transmitters in system 10 are connected to perform in such a manner is entirely conventional, and forms no part of the present invention. In general terms, the transmitters are suitably operatively connected to appropriate sensors which monitor the selected conditions of interest, and which operate to energize the motors in the transmitters to transmit the correct number of rounds.

McCulloh transmitters and the like typically take two different forms-- referred to as normally open and normally closed" transmitters. In a normally open transmitter, the switch which is actuated by the wheel in the transmitter is normally open, and produces pulses by successive closures of this switch with turning of the wheel. Such transmitters, in a given system, are usually connected in parallel with one another. A normally closed transmitter is characterized by just the reverse operation, and in a given system, such transmitters are usually connected in series. The particular transmitters used in system 10 are of the normally closed type, and in this system are connected in series with a battery 22 (or some other suitable source of DC power) and the coil 24a of a relay 24. Relay 24 also includes a normally closed switch 24b which in FIG. 1 is shown open for a reason which will be explained shortly.

Information in system 10 is transmitted over a suitabletwo-conductor line, such as a conventional telephone line. The particular telephone line used in system 10 includes conductors 26, 28. Conductor 26 connects directly with one side of switch 24b. Conductor 28, which is grounded, connects with one side of a battery (or other suitable DC power source) 30--the other side of which is connected through a conductor 32 to the other side of switch 24b. Conductor 26 is connected through a resistor 34 to ground.

System 10 is shown in FIG. 1 with the switches in its transmitters all closed. As a consequence, and because of the series connection mentioned earlier, coil 24a is energized, and holds switch 24b open. Under these circumstances, conductor 26 is essentially at ground potential, or in a 0 state. With operation of a transmitter, it will be evident that switch 24b is alternately closed and opened to produce successive positive voltage square wave pulses (i.e., 1 states) on conductor 26.

The particular different transmitters in system 10 are constructed to produce different coded rounds of pulses, with each round containing three pulse sections. These pulse sections each include on or more pulses. For example, transmitter 18 herein is associated with the numerical code 2-3-1, and when operated to transmit a round of pulses, transmits a round containing a first pulse section containing two time-spaced pulses, a second pulse section containing three time-spaced pulses, and a third section containing asingle pulse. Thus, the number 231 is printed in FIG. 1 on the block representing transmitter 18, as an indicationof its associated code. Transmitter 20 is constructed to transmit rounds with the code 1-4- 3. Accordingly, the number 143 appears in the block in FIG. 1 representing transmitter 20.

Each transmitter in system is intended to transmit pulses having a duration of 0.25-seconds, with successive pulses in a section in a round separated-by, the same amount of time. It is further intended that successive sections in a round be separated by O.5 -seconds, and that successive rounds (when a transmitter is operated to produce a plurality of rounds) be separated by l-second. However, because of the tolerance and operational speed problems mentioned earlier, these times may actually vary within about plus orminus 10 percent.

Considering for a moment FIG. 4,'Graph'A therein illustrates a typical single round of coded pulses produced in conductor 26 by operation of .transmitter 18. As can be seen, thisround includes three pulse sections, indicated by the three bracketsand designated I, II, III. Section'I contains two pulses 36,38, section II three pulses 40, 42, 44, and section III a single pulse 46. The reference character T, indicates the nominal or intended pulse width of 0.25-seconds. It will be recalled that this same time is the nominal or intended time between pulses in a section. The reference character T indicates the nominal or intended time between pulse sections of 0.5-seconds.

In Graph A, an effort hasbeen made'to depict a round of pulses wherein the times, as would be experienced in actual practiceydo not conform to the nominal or intended times. Thus, in section I, pulse 36 is somewhat shorter than, and pulse 38 somewhat longer than 0.25-seconds. The interval between these pulses is somewhat longer than 0.25-seconds. In section II, pulse 40 is somewhat'shorter than, pulse 42 about equal to, and pulse 44 considerably .longer than, 0.25-seconds. The gap between pulses 40, 42 exceeds, whereas the gap between pulses 42, 44 is less than, 0.25-seconds. Pulse 46 in section III-is shorter than 0.25-seconds. Considering the intervals between the pulse sections, both of these intervals are somewhat less than 0.5- seconds.

- Returning to FIG. 1, included in the receiving portion of system 10 is a receiving interpreter, shown generally at 48, which is constructed in accordance with the present invention. Interpreter 48 may be'thought of, and is depicted in FIG. 1, as containing a block of components 50 connected directly to conductors 26, 28, and blocks, such as blocks52, 54, connected to block 50, and-each associated particularly with adifferent one of the transmitters in the system.

Bllocks 52, 54 herein are associated with transmitters 18, 20, respectively, and accordingly, bear the codenumbers 231, 143, respectively. Block 52 is connected to block 50 through multiple-conductor cables represented by the heavy lines shown at 56, 58. Block 54 is connected to block 50 through cable 56 and a cable 60. Other blocks, like blocks 52, 54, are provided for the other transmitters .in the system.

Explaining very briefly, and only in very general terms, how system l0 op'erates. should a breakdown occur in the sprinkler system located at the facility monitored by transmitter .18, this transmitter is immediately operated to produce in conductor 26 a single round of coded pulses, with the code 2-3-1. This transmission is' received by interpreter 48, which functions, as will be explained in detail later, to interpret this transmission correctly as being one from transmitter 18, and as comprising but a single round of pulses. On determining that the transmission was made by transmitter 18, and that it consists of a single round of pulses, block 52, and only block 52, provides one type of an output signal immediately indicating this situa tron.

In the case of a fire at the same location, transmitter 4. Details of the Interpreter The overall construction ofinterpreter 48 is shown in FIGS. 2 and 3, and reference is now made particularly to these figures.

Included within block 50 in the interpreter, such block being illustrated in dashed lines in FIG. 2, and shown in block form therein, are an input circuit 62,

three timers, or timing circuits, 64, 66, 68, a read pulse generator 70, a reset circuit 72, and a pair of counters 74, 76 which are referred to herein respectively as a pulse counter and a section counter. Also included within block 50 are three two-input logic gates including two AND gates 78, 80, and a NOR gate 82.

Timer 64 isalso referred to herein as a code pulse section timer, timer 66 as a code pulse group timer, and timer 68 as an intergroup interval timer. In addition, timer 64, generator 70, and counters 74, 76 are referred to collectively as a code-reading circuit, and timer 68 along with gates 80, 82 are referred to collectively as an interval decision circuit; Further, timers 66, 68 along with gates 80, 82 constitute a pulse-groupspacing-monitoring circuit.

Previously mentioned conductors 26, 28 are connected to the input side of circuit 62--the output of this circuit being connected through a conductor 84 to the input of timer 64, through conductor 84 and a conductor 86 to the input of timer 66, and through conductors 84, 86 and a conductor 88 to the counting terminal of counter 74. Connecting the output of timer 64 and the input of generator is a conductor 90. A conductor 92 connects with the output of generator 70. Connecting conductor 92 with the input of reset circuit 72 is a conductor 94. The output of this circuit is connected through a conductor 96 to the upper input of gate 78. And a lower input of gate 78 in connected via a conductor 98 to the output of timer 66.

Further describing the interconnections existing between components in block 50, gate 78 has its output connected via a conductor 100 to the counting terminal of counter 76. A conductor 102 interconnects conductor 100 and the reset terminal of counter 74. Conductor 98 is connected through a conductor 104 to the input of timer 68, and is connected through conductor 104 and a conductor 106 to the upper input of gate 80. The output of timer 68 is coupled through a conductor 108 to the lower input of gate 82. The lower and upper inputs of gates 80, 82, respectively, are connected via conductors 110, 112, respectively, to conductors 108, 106, respectively. The outputs of gates 80, 82 are connected to conductors 114, 116, respectively.

Input circuit 62, timer 68, generator 70, and reset circuit 72 herein each comprise conventional monostable multivibrators. Circuit 62 responds to a state change from O to 1 on conductor 26, and on such a state change occurring, produces at its output a positive, controlled-duration, square wave voltage pulse, called herein a follower pulse, which lasts about ODS-seconds. Timer 68, generator 70 and reset circuit 72, on the other hand, respond to state changes from 1 to on their respective inputs to produce at their outputs similar positive, controlled-duration, square wave voltage pulses. In particular, timer 68 produces a pulse which lasts about 0.75-seconds, and generator 70 and reset circuit 72 each produce a pulse which lasts about 0.015-seconds.

Timers 64, 66 are similar in construction each comprising a conventional retriggerable monostable multivibrator. Each of these timers responds to a state change from 0 to l on its input to produce a 1 state at its output, which 1 state lasts throughout the application of a 1 state at its input, plus an additional predetermined time interval. More particularly, with the application of a 1 state to the input of timer 64, the output of this timer switches to a l state, and remains therein until about 0.6-seconds after removal of the 1 state from the input. Similarly, with application of a 1 state to the input of timer 66, the output of this timer switches to a I state, wherein it remains until about 1- second after removal of the 1 state from its input. The term retriggerable" as used herein respecting these timers means that a timer may be held in a condition placing a l state on its output, so long as successive O to 1 state changes recur on its input before completion of the time-out" interval for the timer following the last preceding return of the input to a 0 state.

Counters 74, 76 are conventional decimal-output binary counters. Counter 74 is constructed to count from 0-9, inclusive. This counter includes ten separate output terminals (not specifically shown in the drawings) each related to a different one of the ten different counts which may be stored in the counter. To each of the nine of these output terminals which are associated with the counts l-9, inclusive, is connected a separate conductor-all of which conductors are illustrated as a single heavy-line cable 118 in FIG. 2. With counter 74 in a zero-count condition, each of these nine output terminals is in a 0 state. with the other terminal in a 1 state. The counter responds to each state change from 1 to 0 on its counting terminal to change the count in the counter. For example. with the counter in a zerocount condition, on the first such state change occurring on the counting terminal, the counter places a I state on its single output terminal which is associated with the count of one-all other output terminals then being in 0 states. On the second 1 to 0 state change occurring on the counting terminal, the counter places a 1 state on its output terminal associated with the count of two"all other output terminals then being in 0 states; and so on. A state change from 1 to 0 on its reset terminalreturns the counter to a zerocount condition. 1

Counter 76 is similar in construction and operation to counter 74, except that counter 76 includes but three output terminals (not specifically shown) associated with the counts l-3 inclusive. To each of these separate output terminals is connected a separate conductorall of which conductors are included within a cable shown at in FIG. 2. Counter 76 is normally in a condition storing a count of one," with a 1 state existing on its output terminal associated with this count. Its other two output terminals are normally in 0 states. With the first count thereafter made by counter 76, a 1 state is placed on its output terminal associated with the count of two, and the other two output terminals are placed in 0 states. Similarly, when the next count is recorded, a 1 state is placed on the output terminal associated with the count of three," and the other two output terminals are placed in 0 states. On the next count being recorded, counter 76 returns a 1 state to its output terminal associated with the count of one--the other two output terminals then being placed in 0 states. Such operation recurs in cycles with successive counts recorded by the counter.

Continuing with a description of what is shown in FIG. 2, included within previously mentioned block 52 (shown in dashed lines in FIG. 2) are a code latch circuit, or memory, 122, a code matrix 124, a pair of alarm latch circuits 126, 128, and a pair of NOR gates 130, 132.

Circuit 122 and matrix 124 are referred to herein collectively as a code-discriminating circuit. As will be more fully explained later, this combined circuit is programmed herein to respond only to a coded round of pulses transmitted by transmitter 18. As can be seen in FIG. 2, circuit 126 is also referred to as a Condition 1 Alarm Latch Circuit," and circuit 128 as a Condition 2 Alarm Latch Circuit." These two circuits, along with gates 130, 132 comprise an output circuit in interpreter 48. As will become apparent, circuit 126 and gate 130 are employed in the production of an output signal to indicate a transmission from transmitter 18 consisting of but a single round of pulses, whereas circuit 128 and gate 132 are employed in effecting another type of output signal in the case of such a transmission containing more than one round of pulses.

Previously mentioned conductors 92, 114, 116 are connected to input sides of circuits 122, 128, 126, respectively. Also connected to the input side of circuit 122 are cables 134, 136. As will be explained more fullly shortly, cable 134 includes three conductors connected to the output side of code matrix 124. Cable 136 includes three conductors, each connected to a different one of the three conductors previously mentioned in cable 120. A nine-conductor cable 138 connects the input side of the code matrix with the nine different conductors previously mentioned in cable 118.

The output of code latch circuit 122 is connected via a conductor 140 to the upper input of gate 130, and via conductor 140 and a conductor 142 to the upper input of gate 132. Circuits 126, 129 each include a pair of outputs. The lower output of circuit 126 is connected by a conductor 144 to the lower input of gate 130, and also is connected through this conductor and a conductor 146 to the upper output of circuit 128. The lower output of circuit 128 connects with the lower input of gate 132 through a conductor 148, and connects through conductor 148 and a conductor 150 with the upper output of circuit 126. Conductors 146, 148 constitute inhibiting means herein. The outputs of gates 130, 132 are connected to conductors 152, 154, re-

spectively.

Connected with conductors 92, 114, 116, and extending downwardly therefrom in FIG. 2 between blocks 50, 52, are conductors 156, 158, 160, respectively.

As a final correlation between FIGS. 1 and 2, the horizontal portion of cable 56 shown in FIG. 1 includes those portions of conductors 92, 114, 116, and of cables 118, 120, which extend horizontally into block 50 in FIG. 2. The vertical portion of cable 56 in FIG. 1 ineludes conductors 156, 158, 160, and the vertical portions of cables 118, 120, in FIG. 2. Cable 58 in FIG. 1 includes those portions of conductors 92,114, 116, and of cables 136, 138, which extend into block 52 in FIG.

Turning now to FIG. 3, this illustrates details of several of the components shown within block 52 in FIG. 2. Code matrix 124 is shown at the bottom of FIG. 3, and is depicted therein as a rectangular grid of crossed conductors including three vertically extending conductors 162, 164,166, and'nine horizontally extending conductors 168a-168i, inclusive. Where these conductors crossin the matrix, the presence of a black dot indicates a connection between thetwo crossing conductors, and the absence of such a dot indicates the absence of such a connection. Conductors 162, 164, 166 comprise the three conductors mentioned earlier which form cable 134. Conductors l68a-168i comprise the nine conductors mentioned earlier within cable 138.

Appearing to the right of the grid just described, adjacent the right ends of conductors 168a-168i, is a column containing the numbers 1-9, inclusive. These numbers have been included in the drawing to indicate the associations between conductors l68a-168i and the nine output terminals of pulse counter 74. In particular, conductor 168a is associated with that output terminal of the pulse counterwhich is placed in a 1 state with a count of one" stored in the counter; conductor l68b is associated with that output terminal of the pulse counter on which a 1 state is placed with the counter.

which are the three conductors previously mentioned making up cable 136. The lower inputs of gates 170, 172, 174 are connected to previously mentioned conductors 162, 164, 166 respectively.

Conductors 184, 186, 188 are each connected to a different one of the three conductors previously mentioned within cable 120 (see FIG. 2). More specifically, conductor 184 is connected to that conductor in cable 120 which connects with the output terminal of counter 76 that is placed in a 1 state with a count of one stored in the counter; conductor 186 is connected to that conductor in cable 120 which is connected to the output terminal of the counter on which a I state is applied when the count of two" is stored in the counter, and, conductor 188 is connected to that conductor in cable 120 which is connected to the other 7 output terminal of counter 76.

storing a count of two; and so on.Such 1 states on the output terminals of the pulse counter result in 1 states also beiing placed on the respective associated ones of conductors 168a-168i.

It will be apparent that with a matrix such as that just described, programming is possible in accordance with the different codes that may be used by transmitters, simply throughselection of the three locations where crossed wires in the matrix are connected. Matrix 124 is shown programmed for the code 2-3-1 which, of course, is associated with transmitter 18. Thus, connections exist between conductors 168b, 162, between conductors 168e, 164, and between conductors 168a,

Code latch circuit 122 includes four three-input NAND gates 170, 172, 174, 176, and three conventional set-reset circuits shown as blocks 178, 180, 182.

The upper inputs of gates 170, 172, 174, are each connected as shown to previously mentioned conductor 92. The middle inputs of gates 170, 172, 174 are connected to conductors 184, 1,86, 188, respectively,

The outputs of gates 170, 172, 174 are connected to the set terminals, marked S in FIG. 3, of circuits 178, 180, 182, respectively. The reset terminals of these circuits, marked R, are connected together to a suitable manual reset circuit (not shown) which may be operated, as will later be explained, to effect resetting of the circuits. The outputs of circuits 178, 180, 182 are connected as shown to the three inputs of gate 176. The output of gate 176 is connected to previously mentioned conductor 140.

Considering briefly the operation of the set-reset circuits, with such a circuit in a reset condition, a 0 state exists on its output. On a state change from I to 0 occurring at the set terminal of the circuit, the circuit is placed in a so-called set condition, wherein its output is placed in a I state. This situation remains until there is applied to the reset terminal in the circuit a state change from 1 to 0, whereupon the output of the circuit is returned to a 0 state.

Completing a description of what is shown in FIG. 3, previously mentioned alarm latch circuits 126, 128 comprise conventional electronic devices known as clocked-D flip-flops. Such a device typically includes set, reset, clock, and D inputs, and Q and Q outputs. In interpreter 48 herein, only four of such terminals are used, these being the reset, clock and D inputs, and the Q output. The reset inputs are marked by R, the clock inputs by C, the D inputs simplyby D, and the 6 outputs by Q.

Explaining briefly how these devices perform, with such a device in a so-called reset condition, a 1 state exists on the 0 output. With a state change of 0 to 1 occurring at the clock input, the Q output is placed in the opposite of whatever state then exists on the D input. For example, had a 0 state then been present on the D input, the voltage state on the Q output (initially in a 1 state) would remain unchanged. However, had the state on the D input been 1, the 6 output would switch to a 0 state. A state change from 0 to 1 on the reset input returns the device to a reset condition.

The clock inputs of flip-flops 126, 128 are connected to previously mentioned conductors 116, 114, respectively. The reset inputsare suitably connected together to a suitable manual reset circuit like that mentioned above in connection with circuits 178, 180, 182. The D inputs of flip-flops 126, 128 are'connected to conductors 150, 146, respectively, and the Q outputs of these devices are connected to conductors 144, 148, respectively.

The contents of block 54 (see FIG. 1), and of the other such blocks in interpreter 48 which are associated with transmitters in the system other than transmitters 18, 20, are substantially identical with those which have been described as being within block 52. These other blocks differ from block 54 only with respect to the specific programmings provided in the code matrices therein which correspond to matrix 124. In other words, these other code matrices are specially coded to relate to the specific codes associated with the different transmitters in the system. For example, the code maxtrix in block 54 is programmed in accordance with the code 1-4-3. Considering how such programming would affect connections within a matrix, and referring back for a moment to FIG. 3, had such a code been programmed into matrix 124, conductor 168a would have been connected to conductor 162, conduc tor 168d to conductor 164, and conductor 168C to conductor 166.

Finally, also connected to all of the reset terminals in all of the set-reset circuits and locked-D flip-flops in the interpreter, is a conventional, gated, automatic reset circuit (not specifically shown), which responds to each state change from 1 to produced at the output of timer 66 to reset only those devices not then associated with an output block, such as block 52, then producing an output signal. This arrangment positively places all such other devices in conditions properly to respond to succeeding transmissions.

5. Operational Description Explaining now how system and interpreter 48 therein perform, let us assume initially that no transmitter in the system is transmitting. Under such a condition, a 0 state exists on conductor 26, as well as on conductors 84, 90, 92, 96, 98, 108. The outputs of gates 78, 80 place 0 states on conductors 100, 114, respectively, and the output of gate 82 places a 1 state on conductor 116. With respect to pulse counter 74, its nine output terminals which are associated with counts 1-9, inclusive, are in 0 states, and this results in conductors 168b, 1680, 168a placing 0 states via conductors 162, 164, 166, respectively, on the lower inputs of gates 170, 172, 174, respectively. The other output terminal of counter 74 is in a 1 state. In counter 76, only that output terminal associated with the count of one in the counter is in a l state--the other two output terminals each being in a 0 state. Thus, conductor 184 applies a 1 state to the middle input of gate 170, and conductors 186, 188 apply 0 states to the middle inputs of gates 172, 174, respectively.

The 0 state on conductor 92 is applied to each of the upper inputs of gates 170, 172, 174. The 0 state on conductor 114 is applied to the clock input of flip-flop 128. And, the 1 state on conductor 116 is applied to the clock input of flip-flop 126.

The outputs of gates 170, 172, 174 are in 1 states, those of circuits 178, 180, l82 are in 0 states, and that of gate 176 is in a 1 state. The Q and D terminals of the flip-flops are all in 1 states. Consequently, the outputs of gates 130, 132 are each in a 0 state.

Considering what happens if a breakdown occurs in the sprinkler system which is being monitored by transmitter 18, transmitter 18 is operated to produce in the telephone line a single round of pulses, with the code 2-3-1. Such pulses, as they are produced on conductor 26, are represented in Graph A in FIG. 4. It should be appreciated that while each pulse shown in Graph A is represented as a true square wave pulse, in actual practice such pulses might have distinctly rounded corners, and other irregularities causing them to deviate from true square waves.

The positive-going or leading edge of each pulse on conductor 26 causes input circuit 62 to generate a corresponding controlled-duration follower pulse. Such follower pulses are shown in Graph B in FIG. 4, and include pulses 190, 192, 194, 196, 198, 200 which are produced as the result of pulses 36, 38, 40, 42, 44, 46, respectively, shown in Graph A. The time alignments between pulses in Graphs A and B are clearly apparent in FIG. 4. Each pulse in Graph B has a closely controlled duration (shown at T of about 0.05-seconds, as has been mentioned earlier.

One of the important advantages of employing circuit 62 to produce such follower pulses, is that the durationcontrolled follower pulses serve to minimize the potential error-producing effects of the time irregularities present in the actual pulses present on conductor 26.

With initiation of pulse 190, timers 64, 66 are triggered, whereupon they place 1 states on conductors 90, 98, respectively. This situation is illustrated in Graphs C and F, respectively, in FIG. 4 which show the voltage conditions in conductors 90, 98, respectively. This state change on conductor 98 causes a 1 state to be applied via conductors 104, 106, 112 to the upper inputs of gates 80, 82, whereupon gate 82 places a 0 state on conductor 116. This situation is illustrated in Graph H in FIG. 4 which depicts the voltage condition on conductor 116. The output of gate remains 0. No other change of consequence occurs at this time.

The negative-going or trailing edge of pulse causes a state change from 1 to 0 on the counting terminal of pulse counter 74, which action results in counter 74 counting up to a count of one. As a consequence, a 1 state is applied through conductors 168a, 166 to the lower input of gate 174 in code latch circuit 122. However, this state change produces no consequential effect.

Timers 64, 66 remain in conditions with 1 states on their outputs until the occurrence of the next follower pulse, 192, because of the fact that the time intervals between pulses 190, 192 is less than the respective time-out" times of these timers. More specifically, the time interval between pulses 190, 192 is about 0.45- seconds. The time-out time of timer 64, shown at T in Graph C, is about 0.6-seconds, and the time-out time of timer 66, shown at T in Graph F, is about l-second.

Initiation of pulse 192 retriggers timers 64, 66, and their outputs remain in 1 states. The outputs of gates 80, 82 remain in 0 states. The trailing edge of pulse 192 increases the count in counter 74 to the count of two." This change results in the lower input of gate 174 returning to a 0 state, and in the application via conductors 168b, 162 of a 1 state to the lower input of gate 170.

Because of the considerably larger time gap which exists between pulses 38, 40 as compared with the gap between pulses 36, 38, follower pulse 194, which is related to pulse 40, begins too late in time to retrigger timer 64 soon enough to maintain the output terminal of this timer in a 1 state. Referring to Graph B in FIG. 4, the time interval between pulses 192, 194 is about 0.7-seconds. Thus, and as can be seen in Graph C, at

about 0.6-seconds after the end of pulse 192, timer 64 times out, and a state change from 1 to occurs on its output and on conductor 90.

There thus results in Graph C a pulse 202 which serves to .identify and distinguish the completion of a single pulse section (section I) in the round of pulses now being transmitted by transmitter 18. The state change just mentioned which occurs at the trailing edge of pulse 202 triggers read pulse generator 70, which then produces a positive pulse shown at 204 in Graph D in FIG. 4. The duration of this pulse, indicated by T is about 0.0l-seconds.

Pulse 204 places a momentary I state on both conductors 92, 94. As a consequence, there is a momentary situation where 1 states exist simultaneously on all three of the inputs of gate 170. The I state on the upper input of this gate results, of course, from the momentary 1 state on conductor 92. The 1 state on the middle input of the gate results from the I state initially applied, and still applied, via conductorl84 from the outputterminal of section counter 76 associated with the count ofone" in this counter. The 1 state on the lower input of the gate results, as was previously mentioned, from the fact that a count of two" now exists in counter 74.

The result ofthis situation is that a momentary 0 state is applied by gate 170 to the set input of circuit 178, whereupon the output of this circuit switches to and latches in a I state, which is applied to the upper input of gate 176.

Thus, the circuitry just discussed in interpreter 48 has correctly distinguished the first pulse section in the transmission from transmitter 18, has read the number of pulses in this section, which number is stored as the count of two" in counter 74, has compared this number of pulses with that for which the various blocks, like block 52, have been programmed to respond to, and has produced what might be thought of as a memorized response in block 52. It will be apparent-that no such memorized response would have occurred in block 52 had this block been programmed for a first code number other than 2, or had the first-read pulse section contained other than two pulses.

The trailing edgeof pulse 204 triggers reset circuit 72, which then produces a pulse such as that shown at 206 in Graph E in FIG. 4. Pulse 206 has a duration, indicated at T of about 0.0l5-seconds.

As a consequence, a momentary I state is applied to the upper input of gate 78. The lower input of this gate is also now in a I state because of the fact that code timer 66 is still in a condition supplying a 1 state. to conductor 98. The reason for this, of course, is that the time interval between follower pulses 192, 194 (about 0.7-seconds) is less than the time-out time (about I- second) of timer 66. Thus, a momentary 1 state is applied to the output of gate 78, and via conductors 100, 102 to the counting and reset terminals, respectively, of counters 76, 74, respectively. Counter 74 is then reset to a zero-count condition, and counter 76 counts up to a count of two. This change in counter 76 results in a 0 state being placed on conductor 184, and a I state being placed on conductor 186.

The various operations which then take place within the interpreter, as the second and third sections of pulses in the transmission from transmitter 18 are received, are similar to those which have just been described. Thus. and referring to Graph C in FIG. 4, timer 64 produces a pulse 208 which identifies and distinguishes section II, and a later pulse 210 which identifies and distinguishes section III. Throughout the production of these other two pulses in Graph C, timer 66 continues to supply a 1 state at its output, and gates 80, 82 continue to supply 0 states at their outputs.

During receipt of the second section of the transmission, which section contains pulses 40, 42, 44, pulse counter 74 counts up to a count ofthree," whereupon it places a 1 state via conductors 1680, 164 to the lower input of gate 172. As was previously mentioned, because of the fact that section counter 76 now stores a count of two, a I state is applied via conductor 186 to the middle input of gate 172. At the conclusion of pulse 208 in Graph C, read pulse generator 70 is again triggered, this time to produce a pulse 212 which is like pulse 204, and which places a momentary I state on the upper input of gate 172. Thereupon, circuit latches into a condition supplying a 1 state to its output, and to the middle input of gate 176. At the conclusion of pulse 212, reset circuit72 is again triggered, and produces a pulse 214 which is like previously mentioned pulse 206.'Pulse 214 results in the application of a pulse from the output of gate 78 which resets counter 74 to a zero-count condition, and places counter 76 in a condition storing the count of 'three."

Thus, the second section of pulses is identified, read, and responded to in the code latch circuit. Similar action takes place with respect to the third section containing pulse 46. Identifying and reading of this third section ultimately results in circuit 182 latching in a condition applying a 1 state to its output terminal, and to the lower input of gate 176. And, at this time, the output of gate 176 switches from 1 to 0 which state change is sustained and applied via conductors 140, 142 to the upper inputs of gates 130, 132. However, no change as yet occurs on the outputs of these two gates.

The reset pulse which results following identification and reading of pulse section III, resets counter 74 again to a zero-count condition, and returns a count of one to counter 76. Thus, counter 76 is returned to a proper condition for monitoring the first pulse section of another round of pulses.

In the system operation which has just been described, it will be recalled that transmitter 18 transmitted but a single coded round of pulses. Therefore, follower pulse 200 was the last follower pulse to be generated. Accordingly, about l-second after the end of this pulse, timer 66 times out, and returns a 0 state to its output, and to conductor 98. This is clearly illustrated in Graph F in FIG. 4. The state change from 1 to 0 which thus occurs on conductor 98 is applied to the input of timer 68, to the lower input of gate 78, and to the upper inputs of gates 80, 82.

With respect to gate 78 the return of a 0 state to its lower input closes the gate, and, in effect, locks the output of the gate in a 0 state. This assures that counter 76 will remain in the condition to which it has been returned (and which it had initially) storing a count of one. With respect to timer 68, the state change from I to 0 on the output of timer 66 triggers timer 68 into producing a positive voltage pulse shown at 220 in Graph G in FIG. 4, which pulse lasts about 0.75- seconds, indicated by T Thus, there is now a 1 state applied from the output of timer 68 to the lower inputs of gates 80, 82, and a 0 state applied to the upper inputs of these gates. As a consequence, the ouput of gate 80 remains in a state--the state which it has had all along--and the output of gate 82 remains in a 0 state-- -the state to which it was initially switched on initiation of follower pulse 190.

No further action of interest occurs until completion of pulse 220, whereupon timer 68 returns a 0 state to its output terminal, which state is then applied to the lower inputs of gates 80, 82. The output of gate 80 remains in a 0 state. However, and as is illustrated in Graph H, the output of gate 82 is switched from O to 1. Such switching results in clocking of device 126, with consequent placement of a 0 state on its 6 output. This 0 state is applied via conductor 144 to the lower input of gate 130, and via conductor 144 and conductor 146 to the D input of device 128.

A situation now exists with 0 states applies to both inputs of gate 130, whereupon the output of this gate switches from 0 to 1 and applies a I state to conductor 152. Such switching is referred to herein as an output signal from the interpreter of one type, which output signal may be utilized in any suitable fashion to indicate the information just transmitted by transmitter 18. The application of a 0 state to the D input of device 128 ir: hibits this device from producing any change on its Q output should anything effect clocking of device 128. Such inhibiting is important in preventing an improper output signal from now being produced through gate 132. The output of gate 132 remains in a 0 state.

At the completion of such operation, and when the output signal just produced has been noted, the manual reset circuits mentioned earlier are operated to reset circuits 178, 180, 182, and devices 126, 128.

FIG. 5 illustrates what happens in the event of transmitter 18 operating to transmit a plurality of successive rounds of pulses, as in the case of its reporting a fire. As can be seen from a comparison of FIGS. 4 and 5, the operation within the interpreter up through the beginning of pulse 220 is identical in both cases. Immediately following the leading edge of pulse 220:gate 78 is closed by virtue of there being a 0 state on its lower input; a 1 state is applied to the lower inputs of gates 80, 82, and a 0 state to the upper inputs of these gates; and the outputs of gates 80, 82 are in 0 states. Conductors 140, I42 apply 0 states to the upper inputs of gates 130, 132, and the Q outputs of devices 126, 128 apply I states to the lower inputs of gates 130, I32, respectively.

Graph A in FIG. 5, at the right side thereof in the figure, shows the beginning of the next successive round of coded pulses transmitted by transmitter 18. More specifically, this graph shows the beginning of a new section I in such a round, including pulses 222, 224.-

With transmittier l8 constructed as was previously described, the nominal or expected time between successive rounds, shown at T in graph A, is about l-second. However, as can be seen in Graph A, the actual time between the end of pulse 46 and the beginning of pulse 222 is somewhat greater than this nominal time.

For each of pulses 222, 224, circuit 62 produces a related follower pulse, such being shown at 226, 228, respectively, in Graph B. It is the leading edge of pulse 226 which is significant at this time. This leading edge results in triggering of timer 66 to return a 1 state to its output. This is shown in Graph F. Such return of a I state results in the placement of l states on the upper inputs of gates 80, 82. This change has no effect with respect to gate 82, which continues to supply a 0 state at its output. However, in gate 80, its output is switched from O to l, as indicated by Graph I in FIG. 5.

This action, then result s in clocking of device 128 to produce a 0 state on its Q output. As a consequence, a 0 state is applied both to the lower input of gate 132, and to the D input of device 126. Placement of such a state on the D input of device 126 inhibits any change in the I state now existing at the Q output of device 126. Placement of a 0 state on the lower input of gate 132 causes the output of this gate to switch to a I state which is applied to conductor 154. Such switching constitutes another type of output signal from the interpreter, which may be utilized in any suitable manner to indicate the specific information transmitted from transmitter 18.

With noting of this output signal, manual resetting, as mentioned above, is performed.

It will thus be apparent that the interpreter of the present invention, through examining the major time differences which exist between successive pulses transmitted in a system, accurately and reliably discerns different groups or rounds of pulses, different sections within rounds, and the code numbers associated with such sections. For each different transmitter in a system it provides two different discrete outputs for indicating, both, which specific transmitter has transmitted, and what specific information it has conveyed.

The interpreter immediately indicates whether a transmission from a given transmitter comprises one round, or more than one round. Human intervention is not required in the interpreting operation.

While a preferred embodiment of the invention has been described herein, it is appreciated that variations and modifications may be made without departing from the spirit of the invention.

It is claimed and desired to secure by letters patent:

1. An interpreter for use in an electrical signaling system of the type which includes a transmission line and a plurality of coded signalers operatively connected to said line, each signaler being operable selectively to produce and transmit over said line one or more likecoded groups of time-spaced electrical pulses, with each such group including a plurality of pulse sections each containing one or more pulses depending upon the particular code associated with the signaler, with the times between adjacent pulses in a section under all circumstances being shorter than the times between adjacent sections in a group, and with the lattermentioned times under all circumstances being shorter than the times between successive groups produced by the signaler, said interpreter in operative condition comprising a code-reading circuit operatively coupled to said line and constructed to read the particular code of each coded group of pulses transmitted in the line,

a code-discriminating circuit for each different signaler in the system, each operatively connected to said code-reading circuit and operable to indicate a reading by the latter of the particular code associated with the code-reading circuits associated signaler,

a pulse-group-spacing-monitoring circuit operatively coupled to said line and constructed to respond to 17 the transmission therein. of, coded groups of pulses, and to generate, following the completion of such a group, a response of one type if another coded group of pulses follows within a preselected time span, and a response of another type if no such successive group follows within said preselected time span, and an output circuit for each code-discriminating circuit operatively connected thereto and to said pulsegroup-spacing-monitoring circuit, each operable, with its associated code-discriminating circuit indicating a reading of its associated code, to produce an output signal of onetype on said pulse-groupspacing-monitoring circuit generating a response of said one type, and to produce an output signal of another type on the pulse-group-spacingmonitoring circuit generating a response of said other type, 1

each output circuit including meansinhibiting the simultaneous production thereby of both types of output signals.

2. The interpreter of claim 1 which further includes an input circuit operatively connected between said line and said code-reading and pulse-group-spacingmonitoringcircuits for processing pulses transmitted in the line for inputting into the latter-mentioned two circuits, said input circuit being constructed to generate, for each pulse transmitted by a signalerin the system, a time-related, controlled-duration follower pulse.

3. The'interpreter of claim 1, wherein said codereading circuit includes: a timing circuit for discerning and identifying the different pulse sections in a coded group of pulses through monitoring the time spacings between successive pulses in a group to locate a spacing greater. than that expected between adjacent pulses in a section but less than that expected between adjacent sections in a group; a read pulse generator operatively connected to said timing circuit for generating a.

read pulse on the timing circuit identifying a section in a group; a resettable pulse counter operatively connected both to said line and to said read pulse generator. constructed to count pulses transmitted in the line, and to be reset to a zero-count condition on each occurrence of a read pulse; and a resettable section counter operatively connected to said read pulse generator for counting read pulses generated thereby.

4. The interpreter of claim 3, wherein each codediscriminating circuit comprises a memory pro grammed in accordance with the code associated with the code-discriminating circuit, each memory being operatively connected to said read pulse generator and to said counters, and being operable to produce a sustained indication following, but only following, receipt pected between successive like groups transmitted by a signaler; and an interval decision circuit operatively connected to said timing circuit for following the intervals between successive pulse group identifications by said timing circuit, said interval decision circuit effecting generation by said pulse-group-spacing-monitoring circuit of a response of said one type on said timing circuit identifying the beginning of a new pulse group within a preselected interval following its previous identification of a pulse group, and effecting a response by said pulse-group-spacing-monitoring circuit of said other type under all other circumstances.

6. In an electrical signaling system of the type which includes a transmission line, and a plurality of coded signalers operatively connected to said line, each signaler being operable selectively to produce and transmit over said line one or more like-coded groups of time-spaced electrical pulses, with each such group including a plurality of pulse sections each containing one or more pulses depending upon the particular code associated with the signaler, with the times between adjacent pulses in a section under all circumstances being shorter than the times between adjacent sections in a group, and with the latter-mentioned times under all circumstances being shorter than the times between successive groups produced by the signaler, an interpreter comprising a code-reading circuit operatively coupled to said line and constructed to read the particular code of each coded group of pulses transmitted in the line,

code-discriminating circuit for each different signaler in the system, each operatively connected to said code-reading circuit and operable to indicate a reading by the latter of the particular code associated with the code-reading circuits associated signaler, pulse-group-spacing-monitoring circuit operatively coupled to said line and constructed to respond to the transmission therein of coded groups of pulses, and to generate, following the completion of such a group, a response of one type if another coded group of pulses follows within a preselected time span, and a response of another type if no such successive group follows within said preselected time span, and an output circuit for each code-discriminating circuit operatively connected thereto and to said pulsegroup-spacing-monitoring circuit, each operable, with its associated code-discriminating circuit indicating a reading of its associated code, to produce an output signal of one type on said pulse-groupspacing-monitoring circuit generating a response of said one type, and to produce an output signal of another type on the pulse-group-spacingmonitoring circuit generating a response of said othertype, each output circuit including means inhibiting the simultaneous production thereby of both types of output signals.

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4118694 *Apr 29, 1977Oct 3, 1978General Signal CorporationBase loop code transmitter
US4498075 *Sep 23, 1982Feb 5, 1985Napco Security Systems, Inc.Fault indicator apparatus for a multi-zone intrusion system
US4519072 *Nov 10, 1982May 21, 1985Rockwell International CorporationAnswer supervision system
US4611100 *Oct 24, 1984Sep 9, 1986Pacific BellBunching block for McCulloh circuits and method of operation
US4761648 *Dec 2, 1983Aug 2, 1988Racal Security LimitedRemote sensing systems
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Classifications
U.S. Classification340/534, 340/286.1, 340/293, 340/12.17
International ClassificationG08B25/04
Cooperative ClassificationG08B25/045
European ClassificationG08B25/04A