Abstract: The invention comprises a telephone answering device in which a microprocessor controller is coupled to all of the peripheral components through a single common multi-bit data/instruction bus and each peripheral component is coupled to the data bus through a latch which is enabled responsive to an enable instruction placed on a port of the controller.

Abstract: A system for integrating an external numeric keypad with a keyboard on a portable computer wherein the keypad communicates with the system BIOS through the keyboard. The keyboard includes 82 or 83 keys and an internal keyboard controller connected to a switch matrix. The controller repeatedly scans the switch matrix to determine if one or more keys has been pressed and generates scan codes for the active keys which are then output to the computer BIOS. The keypad includes 17 numeric and cursor control keys. The keypad is controlled by an internal keypad controller which is connected to a switch matrix. The keypad controller scans the keypad switch matrix to determine if one or more keys has been pressed and to generate scan codes for the active keys. The scan codes generated by the keypad controller are sent to the keyboard controller through an auxiliary port in the computer system. The keyboard controller converts the scan codes received from the keypad controller into switch locations.

Abstract: An information processing system for processing an application program provides a power control unit being operated at a run mode at which the system is powered and a standby mode at which part of the system is powered. The system further includes functions of inputting any key on a keyboard into an application program, transferring the run mode to the standby mode by pressing a special key on the keyboard, transferring the standby mode to the run mode by pressing any key on the keyboard, detecting no key input takes place for a certain interval of time; and transferring to the standby mode if the detecting means does not detect any occurence of key input for a constant time at the run mode. The system further has function of detecting one key is continuously pressed for a predetermined interval of time and transferring to said standby mode upon detection of one key continuous input.

Abstract: In a remote control unit, a controller is coupled to first and second pluralities of keys for determining which of the keys is depressed at any given time. The first plurality of keys is coupled between a group of drive lines and a group of sense lines. The second plurality of keys is coupled between the sense lines and to an interrupt input port of the controller. A key pressed in the first plurality of keys causes a first kind of interrupt, and a key pressed in the second plurality of keys causes a second kind of interrupt. In response to one of the first and second interrupts, the controller interrogates the keyboard to determine which key is pressed.

Abstract: A self-contained keyboard for computer transmits keystroke data to a host computer via scan codes encoded in a variable magnetic field. In a preferred embodiment the keyboard generates magnetic bursts by electrical current bursts in a loop of a electrical conductor. A receiving loop connected to demodulator circuitry in the body of the computer produces emf spikes according to the magnetic bursts transmitted from the keyboard. The demodulator circuitry reproduces digital scan codes in a register for communication to the computer CPU according to the emf spikes monitored from the receiving loop.

Abstract: A microprocesser-based controller for an appliance such as a microwave oven is able to control a number of different models having different cooking characteristics. The user-operable keypanel is unique to each model, and a scanned matrix keyboard on the keypanel is encoded in a manner consistent with conventional scanned matrix keyboard techniques to identify to the controller the particular model. A scanned matrix keyboard includes a set of drive lines and a set of sense lines intersecting the drive lines. In one embodiment disclosed herein, one or more sense lines are added that are uniquely connected to the existing drive lines depending on the particular model being encoded. The added sense lines are read to determine the model. In another embodiment, one or more drive lines are added, similarly connected to existing sense lines depending on the particular model being encoded.

Abstract: A keyboard for an electronic device includes a first key having a touch surface which, in one mode, is responsive to pressing by a user's finger to indicate a selection associated with the first key, and an array of sensors exposed at the touch surface to detect, in another mode, the location where a finger is positioned on the touch surface as an indication of information to be conveyed by a user. The keyboard also includes a second key having an array of sensors which are exposed at a touch surface of the second key and which are sensitive to manipulations of a finger on the touch surface to provide signals used for switching the first key from the one mode to the other mode.

Abstract: A push-button telephone dialing device for a telephone set has a push-button keypad with a plurality of keys which include a hold function key, and a telephone dialing integrated circuit including a key input signal generator wired to the push-button keypad and producing an appropriate key input signal corresponding to a key pressed on the push-button keypad. The key input signal generator produces a hold function key input signal whenever the hold function key is pressed. The telephone dialing integrated circuit further includes a speech network interrupt circuit which receives the hold function key input signal from the key input signal generator. The speech network interrupt circuit is wired to and controls the operation of a speech network of the telephone set.

Abstract: A memory mapped keyboard controller within a peripheral controller for use in an Industry Standard Architecture (ISA) computer provides a method and apparatus for efficiently monitoring and reading a keyboard switch matrix. In a first mode of operation, the controller activates all the columns and monitors all the rows in the switch matrix to detect when any one or more of the rows becomes active, indicating that at least one key on the keyboard has been pressed. When any row in the matrix is detected as active, then the keyboard controller enters a second mode wherein it selectively activates individual columns and monitors the rows in the switch matrix to detect which row and column contain the activated switch. When the switch location is determined, this location is interpreted by the keyboard controller into a scan code for the ISA computer.

Abstract: A time-shared scanning technique is employed to detect the maximum keys with a keyboard interface. A detecting signal is transmitted, in turn, to the keyboard interface ports in consecutive clock phases. Since every keyboard interface port is independent of each other port, each can detect and record the status of the keyboard except when activated by the detecting signal to transmit a scanning signal utilized to scan all of the other ports. The number of keys that can be detected by the present keyboard interface is about twice that of the conventional keyboard interface.

Abstract: A key scan circuit and the method thereof in a microcomputer is disclosed which requires no diode for preventing circuit short and performs key check or automatic operations with a simplified circuit structure. The key scan method includes a step of designating the input/output mode of a bilateral port by a data direction register in a microcomputer which includes an input/output bilateral port and an input only unilateral port, so as to prevent circuit shorts when more than one key are pushed. Further, by using first and second memories, the key scan method includes a step of determining whether the number of logic low states in the first memory is greater than one, and determining whether the number of logic high states stored in the second memory is greater than one, thus indicating the pressing of multiple keys.

Abstract: A garbling method for 9 non-coded matrix keyboard, and the circuit for performing the method. includesa) connecting at the output each row and column of the keyboard to the outputs of a first register (160) of a parallel to the outputs of a first register (160) of a parallel input-output interface (16), via a circuit (163, 166, 164);b) connecting each row and column of the keyboard to the individual inputs of a second register 162 of the input-output interface.c) randomly setting the order in which the outputs of the first register will be scanned;d) setting at least one of the outputs of the first register at "1" and checking whether one of the corresponding inputs of the second register is at "1";e) if not, scanning the remaining lines one by one by placing them each at "1" until the associated input is at the value "1";f) repeating steps d) and e) to determine the column or row respectively, corresponding to the key of the keyboard that has been depressed.

Abstract: Data acquisition in a multi-function keyboard system includes both acquiring typing data by conventional keyboard scanning techniques and, simultaneously, acquiring pointing data by sampling force sensors coupled to the multi-function pointing key. The keyboard system periodically samples the force sensors to determine bias values defining a null point, and updates the bias values by a moving average calculation to compensate for manufacturing tolerance and long term drift. In response to a start pointing command from the host processor, the keyboard system transmits bias values and then pointing values, the latter being responsive to forces applied to the pointing key by the user for cursor control. The sensor values are encoded so as to pass through to the host processor in a manner transparent to application software. The system scans the force sensors periodically to acquire successive pointing values, and transmits them to the host, as long as pointing mode persists.

Abstract: A key scanning apparatus includes display control circuit for receiving display data and for generating a display control signal which includes display timing periods for driving a display and key scan timing periods for scanning a key matrix. The display timing periods and the key scan timing periods appear in the display control signal in a time sharing manner. The key scanning apparatus also includes a key scan control circuit for outputting a key scan signal to scan the key matrix on the basis of the display control signal and selector for selectively applying either one of the display control signal and the key scan signal to data transfer lines. When the selector outputs the display control signal to the data transfer lines, transfer display data is transferred, and when the selector outputs the key scan signal to the transfer lines, key scan data is transferred.

Abstract: A keyboard apparatus includes a key matrix having key switches disposed at intersections between rows and columns forming a matrix and a control unit for selecting a row and a column of the key matrix to sense a state of a key switch disposed at an intersection of the selected row and the selected column of the key matrix. The apparatus includes a first confirmation unit for sensing, in a first period of time, a key switch state of the key matrix to confirm whether or not two or more depressed keys exist on a row of the key matrix and a second confirmation unit for sensing again, in a second period of time, a key switch state of the key matrix such that when two or more depressed keys exist on a column of the key matrix, a confirmation is made to determine whether or not two or more depressed keys exist on the row on which the key depression is found in the key matrix.

Abstract: A keypad status reporting system provides an indication over a serial bus as to which switch of a plurality of keypad switches is being selected by an operator wherein each keypad switch is coupled between a respective different pair of row and column conductors. The system generates parallel three-bit row and column addresses, combines the row and column addresses to form a parallel six-bit key code, and converts the key code to serial bits of data and places the serial bits of data onto a multiplexed bus in a predetermined channel.

Abstract: A chordal keyboard method and apparatus for generating a key code using a plurality of keys coupled to a controller with a first set of registers and a second set of registers. A user depresses at least one of the plurality of keys. The controller detects, which of the plurality of keys are in a depressed position and which of the plurality of keys are released from the depressed position. The controller sets in the first set of registers and sets in the second set of registers, bit locations of respective depressed keys, and clears in the second set of registers bit locations of respective released keys. When the controller detects that all of the plurality of keys are in a released position, a key code is generated which corresponds to bit locations set in the first set of registers. After generating the key code, the controller clears the first set of registers.

Abstract: A circuit for detecting user contact of one of a plurality of touch pads includes a plurality of drive lines and a plurality of sense lines coupled with the touch pads. A sense circuit responsive to the signals on the sense lines produces a pulse having a width that is proportional to the amplitude of each of the sense signals. A control circuit measures the width of the pulses produced by the sense circuit and compares each measured pulse width to a reference pulse width to distinguish between a touch and no-touch condition for each touch pad. The sense circuit is illustrated in the form of a comparator having a threshold input that is always exceeded by the sense signal to produce the variable width pulse. Separate amplifiers may be provided for each sense line.

Abstract: A keyboard for recording and/or reproducing written information according to the principle of the so-called word typewriter is disclosed. The keyboard has a group of vowel keys in the center thereof, to the left thereof a group of initial consonant keys and to the right thereof a group of final consonant keys. The keyboard of the invention is characterized in that the group of initial consonant keys and the group of final consonant keys both contain substantially all of the consonants and that there are three columns of vowel keys with the center row of keys being hexagonally shaped and the keys in each adjacent column being pentagonally shaped.

Abstract: A signal generator for generating an output signal that is an accurate image of an input signal. A keyboard transmits an input signal and an image controlling device receives the input signal. The image controlling device includes a level variation detecting device which samples the input signal at a sampling rate determined by a sampling period generating device. When the level variation detecting device detects a variation in the levels of a currently sampled value and a previously sampled value it adjusts the image signal accordingly so that the output signal is an accurate image of the input signal. A synchronization signal transmitter transmits a synchronization signal to the keyboard. The keyboard includes a counter which counts the synchronization signal. The counter generates the input image signal that is transmitted to the image controlling device.

Abstract: An improved percussive action electronic keyboard for play as a musical instrument of the type having pivoted playing keys having camming surfaces distal from finger contact surfaces thereof, pivoted hammers having cam follower surfaces for following the playing key camming surfaces, hammer stop for stopping the swing of the hammer in response to depression of its associated key, includes an electronic sensor for generating an electrical signal for each key which is related in amplitude to the pressure with which the key is depressed during play of the keyboard, and a scanning keyboard state monitor connected to said sensor including a keyboard scanner for scanning each of the keys of the keyboard to determine if a key event has occurred, an amplitude comparator for determining when a key depression causes a said key depression signal amplitude to pass predetermined minimum and maximum amplitude threshold values, a scan counter for counting the number of scans occurring between the scans when the key depressi

Abstract: Electronic telephone set, comprising a transmission circuit arranged for being coupled to a telecommunication network and for receiving and transmitting speech signals, a keyboard means comprising a first matrix with respective numbers of intersecting first and second conductors and at the intersections of the first and second conductors key switches coupled to the respective first and second conductors for producing dial information and status information and including a second matrix with one intersecting first and second conductor or a plurality thereof respectively, and having setting circuits conducting current in one and the same direction coupled to the respective first and second conductors at selected intersections of the latter first and second conductors, whereas all second conductors of the second matrix are arranged common to those of the first matrix, and including a control circuit arranged for generating dialling signals compatible with the telecommunication network in response to the dialling

Abstract: There is disclosed a circuit for converting scan data comprising a key matrix switch having multiple keys and multiple mode selecting switches for producing scan data when one of said keys is activated, a scan decoder for decoding said scan data to produce a mode selecting signal, first scan data, second scan data, and first and second clock signals respectively synchronized with said first and second scan data, first and second latch circuits for latching said first and second scan data according to said first and second clock signals, and a mode selecting adder for converting the first and second latched output data of said first and second latch circuits into the first and second converted scan data according to the mode selecting signal of said scan decoder, whereby scan data of a different modes may be produced according to the operation of said mode selecting switches.

Abstract: A keyboard (2) has two transverse arrays of conductors (R0-R13, C0-C7) defining a number of rows and columns of cross-points at each of which a key is positioned whereby depression of a key causes the conductors at the corresponding cross-points to be electrically connected. A scanning device (1) connected to each of the conductors and adapted during a scanning operation to apply a high or low potential to all the conductors of the two arrays and subsequently sequentially to apply a potential of the opposite type to each conductor of one array and to monitor the potential of the conductors of the other array such that if the potential of a conductor of the other array changes, this indicates that the key at the corresponding cross-point is depressed.

Abstract: The present invention is directed to a circuit arrangement for adjustment of the triggering point of the keys in an inductive keyboard. The keyboard consists essentially of a printed circuit board designed in a matrix-like manner, comprising coils superimposed upon each other, into which a ferrite pin plunges when a key is actuated. By the cooperation of a pulse generator with a current switch which can be influenced through control lines, said cooperation being controllable by a microcomputer, a current pulse is coupled from one coil to another coil and is recognized as a readout signal by a controllable readout amplifier and is conducted further to a central unit. The adjustment of the triggering point of the keys is accomplished by varying the steepness of the driving current pulse, for example, by means of a blocking time duration in the charging of a capacitor determined only once, which durations are stored in a table of values, or it is derived from the fundamental interlinked signals of the keys.

Abstract: A control signal generator is disclosed, which is used in a remote control signal transmitter for controlling the circuit operation of an instrument. The generator includes a plurality of key output terminals from which scan signals are outputted and a level detection circuit detecting a level at each key output terminal. The selected one or ones of the key output terminal are coupled to a potential source and the level detection circuit detects the level at the key output terminal during a period except for the scan signal output period, so that a plurality of kinds of custom codes each used for designating the instrument to be controlled are produced by changing the terminal coupled to the potential source and/or by increasing or decreasing its number.

Abstract: A method of and device for selection or entry of a destination in a motor vehicle navigation system. The selection of a destination designation from a stored destination list or the entry of the destination designation is effected by selecting letter positions of the destination designation in a stepwise manner with a first component of a manual input element, and by running the alphabet through, per letter position, at a speed or step size which can be varied as desired until the desired letter is reached with a second component of a manual input element. The acknowledgement of the selected letters or numbers is effected by means of an optical display and, in particular, acoustically by means of vocal output.

Abstract: A method of determining a phantom key condition in an encoder array (10) including (1) enabling each row (R1-R14) of the encoder to a high position; (2) pulling the first row (R1) to be scanned to a low position; (3) scanning the first row (R1) of which in the low position finding whether there is a first key being closed, (4) determining whether there is second key being closed in the first column (C2) of which the first key has been closed, if there isn't a second key being closed, then outputting the signal, if there is a second key being closed, then (5) determining whether there is a third key being closed in the second row of which a second key has been closed before, if there isn't a third key that exists, output the signal, if a third key exists in the second row, (6) then the phenomenon of a phantom exists and the inputting signals will be invalid and beeper sound is emitted to warn the typist.

Abstract: A data input apparatus having a first group of lines extending parallel to one another, and a second group of lines extending parallel to one another and intersecting with the lines of the first group at right angles. The apparatus also has groups of key switches located at the intersections of the lines of the first group and the lines of the second group. The lines of the first group are connected to the output ports of a microcomputer. Low-Level pulses are periodically supplied to these lines at different times. The apparatus further comprises a serial circuit including a group of first resistors each connected between adjacent lines of the second group. A voltage source is connected at a connecting point to one end of this serial circuit through a second resistor. The connecting point of the serial circuit and the second resistor is coupled to the input port of the microcomputer.

Abstract: A smart multiplex scanner system for scanning a matrix of switches utilizes counter of a chosen modulo value that counts to that chosen value for generating row and column enable signals that are used to sequentially scan the switches of the matrix.

Abstract: The system unit of an IBM compatible personal computer generates a distinctive audible "Beep" signal from the system unit's own sound transducer in response to the successful decode of a barcode label in a keyboard emulation data collection device such as a barcode reader. To initiate the generation of such a Beep by the system unit, the keyboard emulation system simulates a benign error condition which does not affect the operation of any application programs resident in the system unit and which does not require any modifications to the operating system or any special device drivers for its proper operation.

Abstract: A keyboard arrangement, such as for a computer or the like, has a number of keys arranged in rows and columns. The keys of each row are associated with a respective conductor and the keys of each column are associated with a respective conductor. Each key, when depressed, interconnects the two conductors. An interrogator is provided to interrogate the rows respectively by transmitting pulses to the rows and to interrogate the columns, to determine the presence of a transmitted pulse. The interrogator is adapted to interrogate the rows in a random or quasi-random order during successive cycles of operation.

Abstract: A method for operating a digital synthesizer type of electronic musical instrument to rapidly make available digital oscillators to produce newly keyed notes even when all digital oscillators are currently active with previous assignments. The method contains a way of maintaining a record of the digital oscillator with the lowest amplitude, and reassigning this lowest amplitude digital oscillator to produce the new note on the rationale that the output of the lowest digital oscillator will be the least missed if an output has to be prematurely curtailed. Beside just a straight amplitude critereon, the method also allows for prioritizing some low amplitude outputs over others to make a more pleasing performance. The invention also includes an apparatus for performing the method.

Abstract: A smart multiplex keypad scanner system for scanning a matrix of switches utilizes a portion of a clock pulse to read the switch status of one of the switches in a matrix of switches in a system in which a standard counter of a chosen modulo value that counts up to a value one less than the number of switches in the matrix is employed to generate addresses of switches in the matrix.

Abstract: An electronic musical instrument having a number of keys, having tone generators capable of simultaneous tone production, the tone generators being smaller in number than the number of keys. The instrument forms an operation for synthesizing a desired waveform, the operation for synthesizing a desired waveform being performed in a repeating cyclic order with an operation cycle and in which the waveform is transferred to the tone generators and read out therefrom at a rate in accordance with the note of a key being depressed to obtain a desired musical waveform. The device includes a number-of-depressed keys detecting device which counts the number of keys which are actuating the tone generator upon depression. A cycle altering device is provided for changing the operation cycle, as a whole, on the basis of the number of depressed keys, counted by the number-of-depressed keys detecting device. The construction allows for a waveform of a smooth temporal variation to be produced.

Abstract: A display can be controlled through one or more thicknesses of glass and one or more air gaps using a transparent keypad through which the display can be observed. The display may be a TV, LCD or other type.

Abstract: A DC bus circuit is disclosed for coupling multiple discrete signals from multiple discrete signal sources with multiple receivers remote from the signal sources. Each multiple signal source has two discrete positions or levels, such as opened or closed, and each signal source has an encoding resistor in series therewith, with no active components. Each encoding resistor has an ohmic value which is a discrete power of two times a reference resistor, and each signal source transmits its signal by grounding or ungrounding its resistor. Each multiple receiver is connected to its corresponding remote signal source by a common DC bus, and each receiver has a decoder circuit which compares the voltage on the DC bus with a reference voltage generated by a pair of reference resistors.

Abstract: A method and apparatus for enhancing the operation of computer keyboards is disclosed. The invention allows touch-typing of nontouch-type keys by detecting a triggering sequence in the touch-type keys. For example, by holding down the Space Bar while depressing and releasing a second key and before release of the Space Bar, the Space Bar is seen to act as a Control key. Furthermore, the functions of nontouch-type keys may be superimposed upon touch-type keys and accessed in a similar manner. The invention interprets make codes which are generated by the keyboard when a key is depressed and a break code which is generated by the keyboard when a key is released. If a triggering sequence of codes is detected, then the normal function of one of the touch-type keys is altered.

Abstract: A data entry keyboard apparatus includes a key switch array (18) in a keyboard unit (12) connected via a cable (14) to a tamper-resistant module (28) which contains control circuitry (16). The control circuitry (16) includes a random pattern generator (30) which generates successive random patterns, causing the selection of a single column and a random pattern of rows, thereby effecting the simulation of key actuations. An EXCLUSIVE-OR gating network (56a-56d) is effective to distinguish a genuine key actuation from simulated key actuations. The invention prevents the ascertainment of actuated keys by unauthorized tapping connections applied to the keyboard unit (12) or the cable (14).

Abstract: A keyboard with capacitive keys is operable through a thick dielectric wall which may be integral therewith. The keyboard may be installed inside an agency or store and coupled to a micro-informatic system providing audiovisual information selected at the request of a passer-by on the street operating the keyboard through a thick shop window. The keyboard includes a base panel (1) made of insulating material provided with Cnm electrodes integrated into the panel. with a free running oscillator being associated with each electrode key. A method of scanning the keyboard is provided.

Abstract: A keyboard with N-key rollover has a matrix of key columns and lines for successively issuing key codes for depressed keys. When first and second keys on the same column are detected as being depressed and then a third key on the same line as one of the first and second keys is detected as being depressed, or when first and second keys on the same line are detected as being depressed and then a third key on the same column as one of the first and second keys is detected as being depressed, a key code for the third key or a key code for a fourth key detected in error upon depression of the third key are prevented from being issued.

Abstract: A control device for cooking apparatus includes an input panel for inputting a desired cooking condition. The input panel includes a flexible panel on which a plurality of cooking condition set key-patterns are formed in line. When a desired cooking condition set key-pattern is pressed, the input panel produces a voltage corresponding to the pressed key-pattern. The value of this voltage is changed step by step from one side key-pattern toward the other side key-pattern on the flexible panel.

Abstract: A key-depression data input device for detecting a depressed key in a plurality of keys arranged in a key matrix, the device including phantom key detection unit for detecting an occurrence of phantom key state, andkey release checking circuit for checking a released key among depressed keys, the releasing of the released key causing a cancellation of the phantom key state. Code data corresponding to the depressed keys being generated and delivered when the key release checking circuit detects that the released key is the key satisfying a predetermined depression-release sequence condition and an error warning being delivered when the key release checking circuit detects that the released key is not the key satisfying the predetermined depression-release sequence condition.

Abstract: A keyboard and keyboard system for use in an electronic device having a plurality of keys. A matrix of keys in rows and columns with each key being defined by an intersection of a row and column wire is used. Either the rows or columns function as initial inputs and the other of the rows or columns function as an initial driver. After a key press, the initial input is changed to a secondary driver and all initial drivers are changed to secondary inputs. The secondary inputs are then read to detect which key has been pressed and the row and the column are connected at the appropriate intersection representing the key which has been pressed. The keyboard system decodes each intersection to define the representation of each key and the representation is communicated to the associated electronic device. A method for detecting input from a keyboard is also disclosed.

Abstract: A digital keypad input device comprises a controller for driving a plurality of I/O signal lines selectively in input, output, and high impedance states. Each line operated in the output state presents an output logic signal that is detected, via a corresponding switch when closed, by another I/O line operated in the input state. Other lines are operated in the high impedance state. The method of the invention enables the number of manual switches to exceed the number of I/O lines.

Abstract: A matrix keyboard system for producing key codes in response to the actuation of key switches. The keyboard system includes ghost key condition detection. In the keyboard system, a group of parallel drive lines and a group of orthogonal parallel sense lines form a matrix, with a key switch being associated with each of the intersection points on the matrix. The drive lines are sequentially activated, and the actuation of a key switch along an activated drive line results in the coupling of a drive signal to the associated sense line. A ghost key condition arises when three of the four corners of a notional rectangle in the matrix contain an actuated key switch. The ghost key condition detector senses the presence of drive signals not only on the sense lines but also on the drive lines, with a ghost key condition being identified if a drive signal is sensed on two or more sense lines and two or more drive lines simultaneously.

Abstract: A data input apparatus comprising a plurality of input keys. A determiner determines whether the time required for executing the function of a pressed key is long or short. In response to the results of determination of the determiner, a first timekeeping device produces a first predetermined time signal, and a second timekeeping device produces a second time signal shorter in duration than the predetermined time signal. A CPU receives data representative of the pressed key at the end of the first or second time signal. In response to receipt of the data by the CPU, a third timekeeping device produces a third time signal shorter in duration than the second time signal. At the end of this third time signal, the CPU receives the data for as long as the key continues to be pressed. The third timekeeping device may include two different timekeeping elements which produce different time signals in order to be used in conjunction with the first and second timekeeping devices, respectively.

Abstract: A matrix-scanning optical keyboard comprising a logical matrix of optical paths between light inlets (3) and outlets (2) with keys disposed on each optical path connecting an inlet to an outlet in such a manner that depressing a key causes a change which can be detected by a scanning driver circuit connected to the light inlets and outlets in order to respond to changes affecting each inlet-to-outlet (3-to-2) coupling by periodically injecting an interrogation signal into each inlet in turn and by inspecting each outlet for the presence of possible changes. The keyboard is capable, for a given emission level, of increasing the sensitivity of the driver circuit to light arriving at the outlets.

Abstract: Apparatus for multiplexing switch state signals comprises a plurality of switches and parallel weighted resistors connected in series between circuit ground and a node at a utilization device. The resistors are weighted as a function of a power of the same base, such as the power of the base 2, for coding the multiplexed switch state signals. A constant current source connected between the node and circuit ground drives current over a single cable conductor through the resistor. Each switch may be independently closed to change the switch state voltage signals multiplexed to the node. An analog-to-digital converter connected between the node and circuit ground demultiplexes the switch state signals received at the node and provides a switch state signal at each analog-to-digital output corresponding to the state of the switches at the moment.

Abstract: A frequency number corresponding to the frequency of a tone intended to be sounded is accumulated in an accumulator at every calculation timing of a constant interval to produce values progressing at a rate corresponding to the tone frequency. At this rate, waveform amplitude value samples are sequentially produced one after another in a tone producing section using the output of the accumulator as phase angle data. A reset circuit is provided in connection with the accumulator and this circuit functions to compulsorily reset the progressing values in the accumulator to its initial value in response to a carry out signal generated at the calculation timing when the phase angle data has reached its predetermined modulo value. Thus the period of progress of the phase angle data is harmonized with the calculation timing, i.e., the sampling timing.