US 3581003 A
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United States Patent Inventors William C. Leone /0 CTL ill/FT 551/504  References Cited UNITED STATES PATENTS 3,056,030 9/1962 H. E. Kelchner 250/209 3,104,388 9/1963 J. W. Balenger l73/17DX 3,334,237 8/1967 J. W. Doosworth et a1... 178/17DUX 3,369,643 2/1968 C. Avgerinos et al 197/98 Primary Examiner-l(athleen H. Claffy Assistant Examiner-William A. Helvestine AttorneyChristie, Parker & Hale ABSTRACT: A keyboard for providing electrical output indications encoded in a preselected code in response t0 the operation of a key. Each key of the keyboard providing a light signal-transmitting path for transmitting light rays from a light source to an optical encoding element for transmission to a photoelectric means to provide the electrical output indications in accordance with a preselected code representative of an operated key. The keyboard includes gating circuit means for controlling the correct pattern of electrical output indications to be produced from the encoding element.
PATENTED HAYZS I971 SHEET 2 OF 5 PATENTEU mam 3581.003
SHEET '5 OF 5 KEYBOARD This invention is directed to an improved keyboard and more particularly to a photoelectric keyboard providing coded electrical output indications.
The present invention is an improvement over our earlier filed applications bearing Ser. Nos. 6l4,l76 and 616,894 both entitled PHOTOELECTRIC KEYBOARD and assigned to the same assignee as the present invention, and both now abandoned. The present invention in particular employs the improved key for use in a photoelectric keyboard as disclosed in the application bearing Ser. No. 616,894.
The present invention is directed to-an improved and inexpensive keyboard and' in particular to a photoelectric keyboard for generating electrically coded output signals in accordance with a preselected code with the operation of each key of the keyboard. The keyboard of the present invention employs the improved key construction of the aforementioned copending patent application for controlling the generation of the binary coded characters. The improved keyboard is constructed and defined to allow a single key to be bivalued, to represent a plurality of characters to be encoded, with a minimum of associated control keys. The keyboard of the present invention advantageously employs photoelectric techniques and optical encoding elements that are commercially available for incorporation into an improved photoelectric keyboard.
From a structural standpoint the invention comprehends a keyboard having a plurality of keys representing different characters movably mounted thereon. Each of the keys being movable to a single readout position for providing an encoded output signal representative of a key character. Associated with the keyboard is an encoding signal source for providing the encoded signals representative of all of the key characters. The encoding means also provides a clock signal in combination with each group of encoding signals for identification of the signal representative of the operated key. Gating circuit means are connected to be responsive to the signals and the clock signals for gating out the correct encoding signal in response to the operation or movement of a preselected key. The gating circuit is arranged with means for correlating the encoded signal provided upon operation of the key with the generation of the encoded signals. The structure described hereinabove is essentially a structural organization for dynamically generating and presenting encoded signals for each of the characters represented by a key on the keyboard including the bivalued keys. Control information is also generated by the encoding means for selecting the specific codes associated with a given bivalued key and is employed in combination with the control keys on the keyboard. The gating circuits, then, are defined as logical gating circuits for identifying the various signals provided by the encoding means for logically controlling the readout of data so that the correct encoded signal is transferred to storage with the operation of a key.
The concept of the present invention also comprehends the static generation of encoded signals by the employment of an encoding element storing a coded pattern for all the characters represented by a key in combination with photoelectric sensing means for generating the signals corresponding to the encoding pattern on the encoding element. When the lightcoupling key is employed on the keyboard, it may be employed to illuminate a particular pattern on the encoding plane for generating the corresponding electrical encoded signals in response to the operation of the key.
These and other features of the present invention may be more fully appreciated when considered in the light of the fol' lowing specification and drawings, in which:
FIG. 1 is a schematic illustration of a photoelectric keyboard embodying the present invention;
FIG. 2 is a portion of an encoding element employed in the photoelectric keyboard of FIG. 1;
FIG. 3 is a schematic illustration of the circuit means for reading out the encoded signals from the keyboard of FIG. I;
FIG. 4 is a schematic illustration of another embodiment of a photoelectric keyboard in accordance with the present invention; and
FIG. 5 is a schematic representation of another type of key adapted for the photoelectric keyboards of the present invention.
The present invention will be described as it may be adapted for use in a photoelectric It should be understood, however, that the concept of the present invention may be employed for constructing an electrical keyboard that does not employ optical techniques. In addition, the invention will be initially described as it may be embodied through the use of the improved key of the aforementioned copending application bearing Ser. No. 616,894. The important feature of the key disclosed in this application is the provision of a light-transmitting channel defined integral with the key and operative for providing a light-coupling action upon movement of the key into the readout or encoding position. Accordingly, the details of the structure of the key will not be described herein and disclosure thereof may be had by reference to the aforementioned application which is incorporated herein by reference.
The keyboard of the present invention comprises a plurality of information keys 10 having the light transmitting channels I0 defined integral therewith as illustrated for the key 10L of the keyboard. It will be understood that the operation of any key 10 is such that with the keys in an inactive condition the light signal is not transmitted through the key to cause the output signal to be generated and only when the key is moved into a coupling position or an encoding position will an output signalbe generated. The information keys 10 for the keyboard include keys having a single value to be encoded, as well as bivalued keys representative of two characters to be coded. For the purposes of identifying the selection of a single character for a bivalued key, the keyboard includes the conventional control keys which are identified asthe control key, IOCTL, and the shift key, 10 SHIFT. It shouldbe understood that these control keys are of the same construction as the information keys ltl. As is conventional in keyboard operation, either one of the control keys are operated when a bivalued key is selected by the operator and neither key is employed when only a single-value key 10 is operated. For the purposes of illustration and convenience in explaining the invention, the information keys 10 and the control keys l0CTL and 10 SHIFT, are illustrated with individual light sources and light sensors although it should be understood that the operation of the photoelectric keyboard may be defined so as to operate from a common light source. As in the aforementioned copending application each of the keys 10 are arranged with multiple light-transmitting elements generally identified by the reference numeral 12 and illustrated in the form of optical fibre elements for transmitting the light rays from the light source 13 to and from the keys 10 via the holder 14. The lighttransmitting elements are arranged in a bundle adjacent the light source 13 and distributed at their opposite ends to the individual information keys 10. There is also provided for each key 10 a further light-transmitting element coupled to the opposite end of the light-transmitting channel 10" defined for the information keys 10 to convey the light rays away from the individual key. The bivalued keys, exemplified by the bivalued key 10', is provided with a pair of light-transmitting channels for transmitting light rays away from the keys for representing the two values. Each of the light-transmitting elements for the single-valued key 10 is similar to the element identified as the element 12D and each has its dark end mounted in an annular holder 14. The pair of light-transmitting channels for the bivalued key 10 are identified by the'reference characters 12 and 12. These light-transmitting elements are mounted separately on the annular holder 14.
The holder 14 is provided with a plurality of apertures 14A for mounting the dark ends of the fibers in a correlated relationship with the signals generated from the encoding pattern, as will be explained more fully hereinafter.
The control keys, CTL and 10 SHIFT, for the keyboard are illustrated with an individual light source and lighttransmitting elements 16 for conveying light rays to and from these control keys. In addition. these control keys are provided with individual photoelectric elements or sensors for responding to the reception of a light signal transmitted through an individual control key. The sensor for key 10 CTL is identified by the reference numeral 17 while the sensor for the 10 SHIFT key is identified by the reference numeral 18. lt will be appreciated that with the reception of a light signal at the sensor 17 and 18, a corresponding electrical output signal will be generated therefrom.
The encoded information generated in accordance with a preselected code is produced through the provision of an encoding element illustrated in the form of an encoding disc 20 mounted on a shaft 21 for a motor 22 for continuously rotating the disc 20 during the operation of the keyboard. The encoding element 20 records the characters represented on each of the keys 10 in terms of binary characters arranged in the pattern of the preselected code. For this purpose the optical encoding element 20 is illustrated in FIG. 2. The encoding information in this instance is recorded in eight tracks on the encoding element for generating binary coded electrical output indications in accordance with the pattern of characters resulting from illuminating the encoding element 20 along a radial segment. This optical pattern will consist of light-transmitting areas arranged with opaque areas for optically reproducing the pattern recorded in the tracks. It will be recognized that the illumination of the encoding element 20 is such that it will be illuminated along a radial section of the disc whereby the binary characters radially aligned in the suc cessive tracks of the encoding element will be representative of a single character to be encoded. In addition, there is mounted on the element 20 a clock track shown as the track 20C arranged adjacent the outer periphery of the disc 20. The clock track 20C consists of isolated light-transmitting areas 20L. The areas 20L are radially aligned with the information tracks or the eight tracks recorded immediately inwardly of the outer periphery of the disc 20 so that each recorded character is provided with a clock area 20L. Accordingly, with the illumination of the segment of the disc 20 representative of a character, there is also provided a light signal corresponding to the clock track 20.
In addition, for correlating the keys of the keyboard with the information generated by the disc 20, there are provided two additional control tracks for generating control information from the disc 20. These tracks 20D and 20E are arranged immediately adjacent the inner information tracks of the disc 20. The track 20D may be considered the control track corresponding to the control key lit) CTL, while the track 20E may be considered the SHIFT track corresponding to the key 10 SHIFT. The control tracks 20D and 20E are necessary when the bivalued keys 10 are employed on the keyboard for identifying or separating the different values for a bivalued key upon operation thereof. Accordingly, tracks 20D and 2015 comprise light-transmitting areas arranged in radial alignment with the pattern of binary characters representing one of the values of an individual bivalue key 10 whereby the single value may be selected upon reading out the encoding element.
The encoding element 20 is illuminated from a light source 23, the light rays from which are distributed by means of a fibre optical distributor 241; (see FIG. 1). The construction of the fibre optical distributor 245 is such that it provides a rectangular output pattern oflight for illuminating the radial section on the element 20 representative of a single character to be encoded. Stated differently, the light distributor 24 functions as a round to rectangular light converter for illuminating the radial section oh the element 20. Arranged on the opposite side of element 20 from the light distributor 24 is a photoelectric sensing element 25. The photoelectric element 25 is arranged in alignment with the fibre optical distributor 24 to receive the light rays transmitted through the encoding element 20. The photoelectric sensor 25 may then be constructed of ll individual sensors for responding to the light signals transmitted through any of the ll tracks recorded on the element 20. Alternatively, the sensor 25 may comprise a sensor of unitary construction having ll sensing segments. The output of the sensor 25, then, is an electrical representation of the pattern of binary characters illuminated on the disc 20, a corresponding electrical binary pattern. It will be appreciated that with the continuous rotation of the disc 20, all of the characters represented on the keyboard are continuously generated at the output of the sensor 25. It is preferable that the encoding element 20 be rotated at a relatively high speed, on the order of 3,600 rpm. so as to provide a time which exceeds the human response by an order of magnitude. At this speed, the successive binary patterns occur every 16.6 milliseconds.
To correlate the generation of encoded signals from the encoding element 20 with the keys on the keyboard, there is provided a keydistribution coupler 26. The coupler 2a is mounted to the shaft of the motor 22 to rotate in unison with the encoding element 20. The key distribution coupler 26 is mounted adjacent to the light exit end of the aperture 14' for the annular element M. It will be recalled that the apertures 14 mount the light-transmitting elements 12D associated with the information keys 10. The location of the dark ends of the light-transmitting elements 12D on the annular element M is correlated with the pattern of the binary characters on the encoding element 20 representing the character on the corresponding key. With the rotation of the light distribution coupler 26, then, the coupler functions to sense the operation of a key 10 by continuously rotating adjacent to the aperture 14 and transmitting a signal therefrom to a light sensor 27 indicating the operation of an information key 10. Stated differently, with the depression of a key 10, a light signal is transmitted from the source 13 through the depressed key 10 and by means of the light coupler 26 to the sensor 27. Accordingly, the output signal from the sensor 27 electrically signals the operation of the key ill) and provides a control signal for reading out the correct pattern of the encoded signals from the sensor 25. In this construction, the keys 10 are considered to be maintained in a depressed condition, once operated, until manually released. It should also be recognized that the light transmitted between the light source 13 and sensor 27 is reversible as indicated in the drawing. Specifically, a light source can be substituted for the sensor 27 while a sensor can be substituted for the light source 13 and the resulting action is identical to that described hereinabove.
With the above structure in mind, the operation of the gating circuit for gating out the correct group of encoded signals will be examined. Each the sensors 17, 18, 25 and 27 has its electrical output indications coupled to an individual amplifier for generating binary output signals corresponding thereto. For example, the sensors 17 and 18 are coupled to a control amplifier 30 and a shift amplifier 311, respectively. The binary output signals from the control amplifier 30 are identified as the signals CTL and @IL In the same fashion, the signals from the amplifier 311 are identified as SHIFT and SHIFT As is conventional in the rotation for binary signals, the unbarred signals, CTL and SHIFT represent the excitation of the corresponding sensor and the barred signal represents the fact that the sensor has not been excited. In the same fashion, the key sensor 27 is employed with a distribution amplifier 32. In this instance, however, only a single output signal is utilized and which signal is identified as the key" signal representative of each depressed key. The sensor 25 is illustrated as having eight output indications each connected to an individual amplifier for storing each of the individual signals from these tracks and which amplifiers are generally identified by the reference numeral 33. These amplifiers are directly connected in parallel circuit relationship with a storage circuit 34 for storing the signals derived from the amplifiers 34 upon command.
It will be recalled that the encoding element 20 and therefore the sensor 25 is adapted to provide clock signals and the control signals CTL and SHIFT. The clock signal associated with each group of information is applied to an amplifier 35 for supplying the clock output signal utilized in the gating circuitry. The amplifiers 36 and 37 associated with the control track and the shift track provide binary outputs. The outputs from the control amplifier 36 are identified as the output signals CTL and m. In the same fashion, the shift amplifier 37 provides'the signals SHIFT D and SHTFT These groups of signals are applied to a logical gating network for identifying the correct group of signals to be read out and in particular utilized to strobe or gate out the information stored in the register 34. For this purpose, the logical gating circuit comprises three AND gates 40, 41 and 42 arranged with an OR circuit 43 for segregating the information received from the encoding element 20. The AND circuit 40 is connected to be responsive to the signals CTL and CTL It will be recognized that these two' signals are representative of the signals that are generated upon the operation of the control key CTL and the signals from the corresponding control tracks for the encoding element 20. This, then, selects the particular group of information associated with the control track D when the key 10 CTL is operated. In the same fashion, when the shift key 10 SHIFT is operated, the signal SHIFT, is generated and is combined in the AND circuit 41 with the information from the track 2015. for generating the SHIFT,, signal. When both of these signals coincide in time, a true output signal is coupled to the OR circuit 43. When a bivalued key 10 is not operated whereby the AND gates 40 and 41 are both disabled, while the AND gate 42 provides a true output signal to the OR gate 43. With he control keys remaining in an inoperative condition, their corresponding sensors 17 and 18 are inactivated whereby the amplifiers and 31 signal this inoperative condition by their false state. The barred signals, then, SHIFT, and CTL, and the corresponding disc signals O I L,, and Shift are all present at the AND gate 42 to cause the four inputs of the AND gate 42 to provide a true signal to the OR gate 43. The outputsignal from the OR gate is combined in the AND gate 44 with the clock signal from the amplifier and the key signal from the amplifier 32. When the input conditions for the AND gate 44 are satisfied, a strobe output signal is applied to the storage circuits 34 for reading out the information therefrom representative of the operated key in accordance with the preselected code. It will be recognized, then, that the strobe output signal is generated as a result of the operation of 1 the control key 10 CTL or the operation of the key 10 SHIFT to separate the characters of a bivalued key. It will also be recognized that AND gates and 41 may be eliminated when the bivalued keys are not employed on the keyboard. Accordingly, the clock and key signals and the AND gate 44 need only be employed for strobing purposes.
With the above structure in mind, the operation of the keyboard should now be apparent. It will be recognized that the operation of the bivalued keys is essentially the same as on a conventional typewriter wherein one of the characters represented on the key is understood to be selected by the operation of one of the control keys 10 CTL or) SHIFT. This type of operation is presently employed on the commercially available photoelectric keyboards manufactured by Friden, Inc. of San Leandro, Calif. and in particular their Model 502 Photoelectric Keyboard. Assuming, then, that the operation of a single valued key 10 or a noncontrolled character from one of the bivalued keys is operated, it will be recognized that the control amplifiers 30 and 31 will signal the false or the barred output signals, CTL and SHIFT Therefore, the gates 40 and 41 will be disabled, while the AND gate 42 will have its input conditions satisfied. Accordingly, a true output signal will be provided from the AND circuit 42 and the OR circuit 43. It will be recognized that with the continuous rotation of the element 20 that each of the information tracks l8 are successively illuminated to provide the encoded electrical output signals from the sensor 25. Along with this information, there is successively generated a clock signal which appears at the output of the amplifier 35 and is successively applied to the AND gate 44. With the correlated rotation of the distribution coupler 26, then, the input-conditions for the AND circuit 44 are satisfied only when the coupler 26 provides the light signal to the sensors 27 representative of the operated information key 10. Since the coupler 26 and the disc 20 rotate in unison and the transmitting elements 12D are positioned at the correct location with respect to the corresponding encoding pattern on the disc 20 the key signal applied to the AND gate 44 will occur at the correct time for providing a strobe signal to the circuit 34 for reading out or storing the correct encoded group of signals corresponding to the key selected by the operator. Stated differently, if an operated key 10 represents the character A" at the time that the information tracks on the disc 20 encoding the character A is illuminated and the corresponding signals appear at the sensor 25, the key coupler 26 will provide the key signal to the AND gate 44 signalling the readout operation. It will be recognized that during this interval the control tracks 20" and 20 are not employed and their corresponding signals CTL and SHIF'T are in the false state as can be appreciatedfrom examining FIG. 2.
Assume now that a bivalued key is to be selected by the operator requiring the control key 10 CTL to be also operated for selecting the desired character for this bivalued key. Accordingly, the bivalued key is operated along with the key 10 CTL. This causes the amplifier 30 to provide a true signal or the signal CTL This signal, then, appears at the AND gate 40. Accordingly, when the disc 20 rotates to the position wherein the control track 20D provides a light-transmitting area, a signal CTL will be generated and applied to the AND gate 40 for satisfying the input conditions of this gate and thereby provide a true signal to the OR circuit 43 and the AND circuit 44. Accordingly, with the application of a true signal from the AND gate 40 to the OR gate 43 and in turn to the AND gate 44, the correct group of encoded signals will be selected when the key signal from the sensor'27' if provided.
This correct identification of the encoded signals results because of the correlation of the location of the light-transmitting element 12D on the element 14 and the corresponding pattern on the disc 20. Withthe delivery of the key signal to the AND gate 44 and the clock signal in coincidence with a true signal from the OR circuit 43 at the time that the CTL signal occurs, the strobe output signal will be generated to read out a correct group of encoded signals from the storage register 34. The same operation will result when a bivalued key is operated in combination with a 10 SHIFT key whereby the AND gate 41 is employed with the OR circuit 43. I
Now referring to FIG. 4, another embodiment of the invention will be described. In this particular embodiment, the encoding signals are generated statically by means of an encoding plate 50 illustrated as an optical encoding plate having an optical pattern for transmitting light in accordance with a preselected code recorded thereon. In this embodiment, as in the previous embodiment, the keys 10 employed are the light coupler keys which transmit light to and from an operated key by means of the light-transmitting channel defined integrally therewith upon depression thereof. Also, the light-transmitting elements 12 are employed for this purpose.
In this embodiment, the light source 13 is coupled through the operated key 10 whereby the exit light-transmitting elements 12D are each provided with an individual fibre optical distributor 52 for providing a rectangular output pattern opposite the optical pattern on the plate 50 representative of the character on the individual key. Only two such fibre optical distributors 52 and 53 are illustrated and it will be understood that all of the remaining patterns on the coding plate 50 are provided with a similar light distributor. Asin the previous embodiment, the keys 10 may be bivalued and the control key 10 CTL and 10 SHIFT are employed for correlating these control keys with the coded information on the plate 50. For this purpose separate tracks are recorded adjacent the eight information tracks in the same general fashion as on the encoding element 20. The control track 50D is arranged adjacent the eighth information track while the shift track 50E is recorded immediately adjacent thereto as illustrated. These tracks are also provided with a light distributor (not shown) for illuminating the light-transmitting sections of the tracks 50D and 50E with the operation of the corresponding control keys. To generate the electrical output signals, a sensor array 53 is provided and which array has the same general configuration as the coding plate 50. The sensor array may consist of 10 sensing strips for each track shown on the coding plate 50. No clock track is necessary in this embodiment as the information is statically generated rather than dynamically. The electrical output signals then are derived from the array 53 in accordance with the operation of a key 10 or a key M) and a control key. It will be recognized that with the operation of a key 10, a light signal will be coupled by means of a light-transmitting element 12 from the source 13 through the coding plate 50 to provide a coded group of light signals to impinge upon the individual sensors of the sensing array 53 for producing corresponding groups of electrical output signals. With this arrangement, it will be recognized that with the depression of a bivalued key, both values are encoded if a control key is also depressed. This separation of values may be effected through gating circuitry of the type described in H0. 3. This gating circuitry would select one of the values as a result of the provision of the control signals derived from the tracks 50D and/or 505.
With the above structure in mind and referring to FIG. 5, another type of key useful in the invention will be described. The keys 10 described hereinabove function to couple light between the lighbtransmitting channels 12 by means ofthe integral channels 10. The present key 50 effects the same function without employing an integral light-transmitting channel.
The keys l are considered as a light-interrupt type of keys. The construction of the key is such that it interrupts the light path between light-transmitting elements when in an inoperative or nondepressed condition and allows light transmission through an air path when in a depressed condition to couple the light rays between light-transmitting elements. For this purpose the keys 50 are provided with a light-interrupting element or prong 50 integral therewith and dependent from the body of the key, as illustrated. The tip of the element 50 engages a leaf spring 51 in its normal inoperative or nondepressed condition. The end of the leaf spring is upturned and is secured in a locking notch 52 provided for the spring 51. The upturned end of the spring is identified by the reference numeral 51. Assuming that the keys 50 are bivalued keys, a pair of exit light-transmitting elements 53 and 54 are illustrated on one side of the element 50" and the entry light-transmitting element 55 is arranged on the opposite side of the element 50". The construction of the element 50 is such that it interrupts the light path between the element 55 and the elements 53 and 54 in its normal nonoperative condition, as illustrated. When the key 50 is depressed, the element 50'" is removed as a light interrupter and the light rays from the light-transmitting element 55 travel through a short air path to the light-transmitting elements 53 and 541. As long as the key 50 is depressed, this condition prevails. With the depression of the key 50, the spring Si is depressed and is unlocked from the notch 52 With the release of the key 50 the spring urges the key 50 back into its light interrupting condition and is maintained in that condition through the interlocking of the spring end 51" and the notch 52.
It should be appreciated that the key 50 can be substituted for the keys l0 and the invention can be practiced, as described hereinabove.
What we claim is:
1. In a keyboard for providing electrical output indications encoded in a preselected code in response to the operation of a key on the keyboard including a keyboard having a plurality of movable keys thereon, one
key for each character to be encoded, each key being further characterized as providing a light signal transmitting path therethrough,
a li ht source in ividual light-transmitting elements for transmitting light rays from said source to and from an individual key he means thereof upon operation ofthe key,
means for mounting the dark ends of the individual lighttransmitting elements in a preselected configuration,
a rotatable optical encoding element having the characters of each key for the keyboard recorded thereon in accordance with the preselected code,
a key distribution light-coupling means,
means for rotatably mounting the optical encoding element and the light-coupling means to allow them to continuously rotate in unison,
means for distributing light from said source onto the optical encoding element,
photoelectric means for providing electrical output indications in accordance with the light rays transmitted through the optical encoding element,
said photoelectric means being arranged to be responsive to the light transmitted from said source through the keys and the light-coupling means, and
gating circuit means connected to be responsive to the out put indications from the photoelectric means for controlling the correct pattern of binary characters to be produced in accordance with the operated key of the keyboard.
2. In a keyboard as defined in claim ll wherein the optical encoding element records readout control information for each group of encoded binary characters and the gating circuit means is responsive to the corresponding readout control information and the signals from the light coupler.
3. in a keyboard as defined in claim 2 wherein the means for mounting the dark ends of the light-transmitting elements comprises a ring having the elements located thereon in posi tions correlated to the recorded group of information on the encoding element.
4. In a keyboard as defined in claim 3 wherein the keyboard includes bivalued keys and control keys constructed and defined for providing a light signal transmitting path therethrough,
individual light-transmitting elements for transmitting light rays from said source to and from the control keys upon operation thereof,
said photoelectric means being responsive to the operation of the control keys for providing a corresponding electrical output signal and said gating means comprising logical" control circuits for defining control signals for controlling the readout of the correct pattern of binary characters including when the bivalued keys are operated.
5. In a keyboard as defined in claim 4 wherein the control keys include a shift key and a control key and the optical encoding element includes a clock track for providing a clock signal on readout with each group of encoded characters and control and shift signals for preselected groups of characters correlated to the bivalued keys.
6. In a keyboard as defined in claim 5 wherein the gating means comprises three AND" circuits for signalling the operation of a shift key, a control key or neither key for combination with the clock signals and the signals from the light coupler.
7. In a keyboard as defined in claim 6 wherein the lighttransmitting elements are fiber optic elements.
8. In a keyboard as defined in claim 7 including storage circuit means for storing the encoded signals from the photoelectric means and the signal from the gating circuit means being applied thereto for reading out the correct group of signals.