Abstract: A manually controllable switch provides a user with an "analog feeling" for controlling digital electronics. A plurality of first electrical conducting portions are alternately arranged with a plurality of second electrical conducting portions. Physical spacing between electrical conducting portions is proportionally and symmetrically varied to provide a sequence of logical states upon movement of the manually adjustable control knob. An electrical contact on the control knob moves into and out of engagement with the electrical conducting portions. Contact between the contacting portion and the conducting portions causes changes in logic state as recognized by a microprocessor or dedicated circuitry coupled to the conducting portions. The microprocessor or dedicated circuitry recognizes specific sequences of change in logic state as indicating manual movement of the control knob.

Abstract: A CRT touch screen having raster-generated light patterns at the viewing screen borders of a conventional CRT. Reflective surfaces proximal to the screen borders reflect the light patterns across the CRT surface to external photodetectors. Modulating the horizontal blanking signal or employing periodic non-reflective patterns on the reflective surfaces effects raster-generated light patterns having a unique time frequency higher than the vertical synch frequency, but lower than the horizontal synch frequency. A screen pointer blocks the lights patterns reflecting across the screen to two or more of the photodetectors. The blocking is time-relative to the CRT's horizontal and vertical synch signals. The photodetector outputs are bandpass filtered at the unique pattern frequency to suppress electromagnetic interference from the CRT's horizontal raster synch, the CRT's vertical synch and other electromagnetic and optical sources.

Abstract: The interrupt-driven keypad scanning method and apparatus accurately interprets keypresses in single-keypress applications. Initially, interrupts (16, 26, 36, 46) associated with each column line (10, 20, 30, 40) of a keypad matrix (70) are set to trigger when a key is pressed. Once an interrupt triggers, a microcontroller (99) polls the row lines (15, 25, 35, 45, 55, 65) to determine which key, if any, was validly pressed. If exactly one keypress is detected, the keypress is valid. Next, the interrupt for the valid key's column line is enabled while the other column line interrupts are disabled. When a next interrupt is received, the keypad returns to the row-scan state for determination of which keys are depressed. If no keys are depressed, which occurs when the validly-pressed key has been released, the keypad returns to the keypress-detect state. The method also interprets pathological keypresses such as key rollover, multiple keypresses, and key mis-hits.

Abstract: The padless touch sensor is used for detecting a touch at a sensing location onto a dielectric element by a user coupled to earth. The sensor comprises a conductive plate attached under the dielectric element and in registry with the sensing location. A predetermined potential is applied on the conductive plate. Simultaneously, test pulses are produced into earth. When the user touches the dielectric element at the sensing location, a potential variation in the conductive plate is produced during a test pulse due to a capacitive circuit formed between earth, the user and the sensor. No deposition of conductive pads on the dielectric element or other special processes are required. Foreign matter or objects placed directly on top of the dielectric element will not erroneously produce a touch condition.

Abstract: A trim unit having a simple structure is provided which has an arrangement such that an automatic repeating function is activated when a trim switch is depressed continuously. If a determination is performed in step S40 that count value CNT (1) of a first counter is larger than N3, then the value of CNT (1) is set to N2+CNT (2) so that count value CNT (2) of a second counter is increased. Then, the trimming position is moved by one step in step S80. If the trim switch is continuously depressed, the interval for the count value CNT (1) to be larger than N3 in shortened in accordance with the count value CNT (2). Thus, the repeating speed for the trimming position to be moved is raised so that the trimming position is quickly adjusted.

Abstract: A selective call radio (10), including a housing (12), has a display (18) and touchpad (22) of the same size. The display is mounted to a surface on one side of the housing, and the touchpad is mounted to another surface on an opposite side of the housing, directly opposite the display. A screen surface of the display and a touch surface of the touchpad are parallel and have a same number of edges. Sliding of a user's fingertip on the touchpad in a right-to-left direction causes movement of a pointer (26) in a left-to-right direction, and vice versa. Movement on the touchpad causes movement in an identical amount on the display.

Abstract: A scanning apparatus for uniquely identifying an actuated key on a keyboard and an actuated location in a drawing tablet. The scanning apparatus includes independently actuatable switches associated with the keyboard. The scanning apparatus also includes vertical and horizontal conducting traces juxtaposed one to another and electrically connected to a horizontal and vertical resistive bar, respectively, associated with the drawing tablet. The switches and traces are energized under control of the apparatus such that portions of each can be actuated by a user resulting in the generation of unique analog signals indicative of the particular key and particular location upon the drawing tablet actuated by the user. These unique analog signals are converted to digital signals for further processing.

Abstract: In an electronic musical instrument which generates musical tone signals based on playing information input from a key switch circuit 10, a key scan circuit 11 includes a decode circuit 22 to which the current status information and the previous status information read out from a scan data memory 21 are input, and if status information which cannot be processed is input, the decode circuit 22 converts it to status information which can be processed, and if there is no empty space in an output data buffer 24, the decode circuit 22 detects no status change. Such construction allows malfunction to be prevented with a simple construction.

Abstract: An encoding method employs sixteen basic values, twelve numerical magnitudes and four directional modifiers. These values are the result combining binary digits in sets of 4 bits. The encoding method is utilized for encoding letters, symbols and programming commands. Letters are defined as numerical magnitudes altered by a directional modifier, symbols and commands are addressed as numerical magnitudes altered by two or more directional modifiers. An analog to digital encoding technique converts analog data into binary form by means of "breaking" an analog wave into a multitude of periodic waves, each wave with a particular wave-break, wave length and amplitude, supplying hence, an efficient and economical method for processing and storing binary information. An analog device describes the particular position of the sun at a given time, supplying therefor an apparatus that not only measures time but also describes space.

Abstract: A remote control transmitter has a kill mode in which less power is drawn than in the full power operating mode. The transmitter has a stop mode in which minimal power is consumed. The stop mode is entered whenever no keys are being depressed. The device stays in the kill mode whenever a key closure is maintained for longer than a predetermined time.

Abstract: A modular computer has a framework with module bays for receiving CPU modules, power modules, and peripheral function modules such as floppy and hard disk drives. The framework has a built-in compressed bus and a variety of function modules which can be plugged into any one of the module bays. Function modules include, but are not limited to, CPU, power, floppy disk, hard disk, RAM memory, LAN communication, modem, FAX communication, and data acquisition. In some embodiments function modules are provided for communicating with separate input means, such as voice, keyboards, and pen-pads. In one aspect the module bays and the function modules are configured according to dimensional and connective standards of the Personal Computer Memory Card International Association. In another aspect a modular portable computer has a flexible, rollable, keyboard with a system for transmitting keystroke signals by magnetic induction.

Abstract: The present invention is directed to a system and methodology where virtually no DC power dissipation is used during keyboard scanning or key closure. This is done by replacing the passive pull-up (or pull down) resistors of previous schemes by input/output (I/O) circuits with repeaters and utilizing a scanning protocol and methodology which take advantage of the bidirectional I/O devices with repeaters. In a preferred embodiment, a plurality of CMOS bidirectional I/O circuits with repeaters are used, one for each row and column line in a switch matrix. A low power, switch activation scanner circuit determines activation of a switch. The circuit is coupled to or may include a plurality of switches, arranged in rows and columns, each row output line intersecting each column output line at a different node, for coupling a first row to a first column at a first node when a first switch of the plurality of switches is activated.

Abstract: A compound type keyboard detector is disclosed. It comprises a time-sequencing generator, a keyboard scanner, a column input port and a row input port, a column lock and a row lock, a keyboard-synchronization detector, a keyboard detector and a keyboard decoder. With the unique design of the keyboard detector in conjunction with the various circuits that are associated therewith, a given number of pins can be used for a relatively greater number of input keys, or a smaller number of pins can be used for relatively complicated input keyw. This type of keyboard detector is good for small IC products, and can reduce the manufacturing cost thereof.

Abstract: Scan code generation for portable personal computers (PCs) using a matrix keyboard operates to produce keyboard output scan codes corresponding to IBM.RTM. compatible PC/AT scan codes. Key numbers are assigned to one or the other of two classes (simple and complex). Two classes of scan code translation tables (simple and complex) are stored in memory, either ROM or internal RAM memory. Whenever a simple key is operated, the simple table is accessed. The complex scan code table is addressed, in accordance with a set of seven edit rules, utilized in conjunction with the state of operation of multiple keys on the keyboard, to determine the appropriate translation. All of the logic needed to generate the necessary scan codes is collapsed into a structured table-driven mechanism.

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 method and system are disclosed for processing input to a data processing system having a memory and an input device having a number of keys which represent associated characters and functions. According to the method of the present invention, a translation table is created within the memory for translating virtual key codes, which specify relative positions of associated keys, into corresponding input codes, which specify a character or function. The translation table enables virtual key codes to be translated into character codes independently of the operating system and input device utilized by the data processing system. In response to the detection of a selection of a key of the input device, a scan code representing the selected key is determined. The scan code representing the selected key is then converted into a virtual key code, which is translated into an input code utilizing the translation table. The input code is thereafter received for processing within the data processing system.

Abstract: On word starts, the system displays sets of very frequent words and attributes in locations which associate them with input actions. Possible attributes include letters, phonetic sounds, character strokes or parameters as appropriate for the language. Attributes inputted select word sets from a vocabulary which has N sets of a plurality of word sets in which the words of each set share a unique set of one to N attributes. The display presents accessed word sets which the user may search for wanted words. Vocabulary words include codes to select inflection sets when they are selected. For alphabetic languages, spelling rules and a store of modified word ends and inflection starts are used in the application of inflections. Selected words, with or without inflections, are outputted by input actions which may append `Space` or punctuation endings. User actions on keyboard and/or stroke sensing apparatus input attributes and select, inflect, and output words with endings.

Abstract: A keypad scanner for a keypad having a plurality of keys which may be pressed into a down state includes circuitry for detecting when no or any key is pressed down and thereupon generating a no or any key down signal, circuitry for detecting when more than one key is pressed down and thereupon generating a multiple key down signal, and an interrupt generator coupled to the aforementioned circuitry. The interrupt generator itself includes circuitry for detecting a change in no or any key down signal level, circuitry for detecting a change in multiple key down signal level, and circuitry for generating an interrupt signal when either the circuitry for detecting a change in no or any key down signal level or the circuitry for detecting a change in multiple key down signal level detects a change.

Abstract: A circuit for encoding and decoding key input data from a matrix of switches with a single transmission wire. The circuit for encoding and decoding key input data with a single transmission wire includes a control circuit, a charge storage circuit and a keyboard matrix circuit. The keyboard matrix circuit is composed of a group of resistors connected in series. Each resistor is coupled to ground via a manually actuated switch. When one of the switches is actuated or closed the switch provides an electrical path to ground through the resistors that precede the switch and shorts the resistors that follow the switch. When one of the switches is closed the charge stored on the charge storage circuit dissipates through the electrical path to ground provided by the actuated switch, at a rate related to the sum of the resistance preceding the switch.

Abstract: A multi-purpose keyboard controller includes a matrix keyboard control circuit, a serial keyboard control circuit, a PC/AT port control circuit, and an external interface for RTC control. These control circuits are coupled in parallel with the interface logic of the computer system and use the built-in SMI interrupt mechanism of the computer system for reading and writing the keyboard or capturing keypress events. Software BIOS setup is employed to select one of the keyboard control circuits for utilization with the particular personal computer with which the system is employed. The interrupt scheme used by the keyboard interface uses SMI interrupts to the processor and SMI based software routines to read and write the values to and from the keyboard, thereby eliminating the need for dedicating a special hardware interrupt level; so that the system remains compatible with the DOS PC/AT Port 60/64h software interface.

Abstract: A computer input device, i.e. a keyboard, employs a reduced number of keys for entering words, numbers and commands. A novel and economical data encoding technique is employed which assigns single four bit code words (known as quytes) to the Arabic numerals 0-9, two quytes to the letters of the alphabet, and three or more quytes to various "software key" represented commands. This encoding technique not only decreases memory space requirements, but also increases processing speed. To enable an operator to select virtually any number of software keys, a plurality of additional function keys is provided, and these can be operated in a sequential manner along with the arrow and comma keys to generate a software key comprised of any number of quytes. The end of a software key is signified by the actuation of a letter key. Each software key can be represented by an icon which graphically combines all of the key symbols that are necessary to invoke it.

Abstract: An improved energy-saving keyboard with low parts count accomplishes a sophisticated regime of low-power mode intervals in response to key closures and communications from the computer to which the keyboard is connected. An interrupt pin of the keyboard controller (encoder) prompts the transition from low-power mode to normal mode. The communications from the computer is synchronous communications mediated by a clock line, and the interrupt pin is tied not to the clock line but to the data line of the synchronous channel. The interrupt pin is also tied to a resistor array providing pullup biases to the keyboard matrix; in normal-power mode a discrete output of the encoder forces the common point of the resistor array to a fixed voltage level. In low-power mode, on the other hand, the discrete output is not asserted, and the resistor array is pulled high by a pullup impedance of relatively high resistance to the fixed voltage level. In this way, any key closure at the keyboard triggers the interrupt.

Abstract: An information input device is provided comprising a connecting matrix, a voltage source, a probe pin coupled to said voltage source, a first multiple channel delay circuit, a second multiple channel delay circuit, a NOR circuit with multiple inputs, a first pulse generator having a trigger input connected to an output of said NOR circuit and a reset input connected to the output of said first multiple channel delay circuit, and a second pulse generator having a trigger input connected to the output of said NOR circuit and a reset input connected to the output of said second multiple channel delay circuit.

Abstract: A touch control system that is responsive to a user input selection includes an electrically non-conducting substrate, such as glass ceramic, and at least one capacitive-responsive touch pad on the substrate. A source signal having a primary frequency that is greater than 150 kHz, and preferably in the range of between 150 kHz and 500 kHz, is applied to one portion of the touch pad. The touch pad couples the electrical signal to another portion of the touch pad in order to develop a detection signal, which is decoded in order to determine the presence of the capacitance of a user. The decoder preferably includes a peak detector composed of a low gain circuit in order to avoid distortion of the detection signal. Greatly improved performance in the presence of liquids, such as water, on the touch pad is provided. This is especially useful when the touch pad is applied to a horizontal surface, such as a cook top, upon which liquid spills may occur.

Abstract: A scanning method of keypad architectures utilizing power pin V.sub.DD and ground pin GND of an integrated circuit device is disclosed. The integrated circuit device has a number of row pins and column pins, a power pin and a ground pin, and a number of pins for other functions of the integrated circuit device. The row and column pins, power pin and ground pin of the integrated circuit device are connected to respective connections of a keyswitch matrix, which has a plurality of row connections and column connections. The keyswitch matrix of the scanning apparatus has a first one of the row connections connected to the power pin. The keyswitch matrix of the scanning apparatus has a second one of the row connection connected to the ground pin. Each of the other row pins is connected respectively to corresponding one of the row connections. Each of the column pins is connected respectively to corresponding one of the column connections.

Abstract: A fault tolerant method of decoding an electronic key system includes the steps of reading a key return image from one or more actuated keys and comparing the read key return image to the previous key return image. The method also includes the steps of determining the actuated key from a net key return image between the read key return image and the previous key return image.

Abstract: A keyboard scanning circuit for detecting additional user selected functions on a keyboard while the keyboard is being "debounced". The scanning circuit permits the scanning for additional functions without the need for additional scanning ports by detecting whether a row port of the scanning circuit is connected to a source voltage via a resistor, a ground via a resistor, or is floating. The user or the manufacturer using the circuit can set the switches which establish the status of these additional functions.

Abstract: A method and apparatus for detecting the added functions of a telephone dialer by adding diodes to the IC circuit and using as part of the input pins such that the need for total number of input pins and thus the manufacturing costs of the IC are reduced. The method is executed by using the available keyboard input/output boards without increasing the need for extra input pins in order to detect whether there is any diode in existence that is connected among the input/output ports.

Abstract: A keypad encoder is used with a keypad having an array of keys arranged in columns and rows. Depressing any key on the keypad closes a corresponding switch, coupling one of the columns to one of the rows. The keypad encoder includes a resettable logic circuit that generates a control signal having first and second states that control the mode of operation of the keypad encoder. A scanning circuit asserts a scanning signal on the columns of the keypad in a predefined sequence when the control signal is in the first state and asserts the scanning signal on all of the columns of the keypad simultaneously when the control signal is in the second state. An encoder circuit identifies which row, if any, has a closed switch in any of the keypad columns on which the scanning circuit has asserted the scanning signal.

Abstract: An apparatus for and method of scanning a key array (101-116) uses two or three scan lines (134 and 135 or 308, 309, and 310), thereby limiting the need for an excessive number of input/output lines of a processor (136). A separate resistor ladder (301,302, 303) is provided for each dimension of keys, including row, column, and/or matrix. A minimal number of parts is also required to implement the resistor ladder (301,302, 303). A reference conductor (311), a row conductor (312), a column conductor (313), and, if desired, a matrix conductor (314) each run under each key, such that when a different key is depressed, a unique combination of voltages appears at the scan lines (134 and 135 or 308, 309, and 310) for the resistor ladders (301, 302, 303).

Abstract: A computer has an operating system with a graphical user interface. This computer also has a key manager for graphically associating objects, such as data or application programs, with keystrokes, such as Fn-Fx key combinations, where Fn is a special shift key and Fx is a numbered function key. A key group or folder contains icons which represent objects. This key group can be built or modified by the user by copying an icon contained in another program group or folder via a drag and drop or similar operation. The key manager interrogates the operating system for the contents of the key group, and receives a key array. The key array contains objects associated with keystrokes. The key manager then monitors the operating system for any keystrokes received from the user. Upon receipt of a keystroke, the key manager determines whether the keystroke is in the key group.

Abstract: A key signal input circuit for a microcomputer including a microprocessor and a single input port. The microcomputer outputs, in sequence at a constant interval, a plurality of grid signals, receives different key signal inputs successively through the single input port synchronously with the grid signals, and discriminates the inputted key signals to recognize which keys have been selected. The key signal input circuit includes a power supply circuit, responsive to the grid signals from the microcomputer, having a plurality of power supply lines for supplying, in sequence at a constant interval, a desired power through the power supply lines. A key matrix circuit having a plurality of sets of keys, responsive to the desired power through the power supply lines from the power supply circuit and to on/off states of the keys, coupled, by sets, respectively to the power supply lines. The key matrix circuit applies the key signals successively to the microcomputer.

Abstract: A keypad scanner mechanism which may be incorporated with an integrated circuit including a microcontroller. The keypad scanner mechanism includes a keypad with more than one key. The keypad scanner mechanism has an activity detect mode and a normal mode. In the activity detect mode, the keypad scanner mechanism wakes up the integrated circuit and triggers the normal mode. In the normal mode, the keypad scanner mechanism identifies and reports to the microcontroller the depression of keys on the keypad. The keypad scanner mechanism also includes a means for debouncing, a multiple keys down code, and a no keys down code. The keypad scanner mechanism is suitable for any keypad application, however, it has been found that the keypad scanner mechanism is especially suitable for incorporation into the base and handset units of a cordless telephone that integrates the speech, control channels, and microcontroller portions of a modem, and the man-machine interface functions of a cordless telephone.

Abstract: An adaptive keypad which has one or more keys includes, for each key, a pressure transducer positioned below a semi-rigid faceplate where the pressure transducer has a resistance which decreases as the pressure compressing the transducer increases. The transducer is connected in series with a capacitor to define an RC circuit for each key. Each RC circuit has a charge time proportional to the pressure applied to the key. A time capture circuit initially and thereafter intermittently, obtains the charge time for each RC circuit for each key and computes a conductance value from that time. The initial conductance value is stored in a memory. A comparing circuit intermittently compares the initial conductance value with each subsequent conductance value generated for a key. If the comparison value generated is greater than a predefined amount, a signal is generated indicating that a key has been depressed.

Abstract: A capacitance-sensitive switch unit including a capacitive element operable to produce an effective capacitance dependent upon the physical proximity of objects relative thereto, a first selector signal input connected to the capacitive element to enable a first input signal to charge the effective capacitance, a threshold signal producing circuit connected to the capacitive element, for producing a threshold signal which is rendered active when the effective capacitance charges to a pre-defined potential, a switching circuit for selectively connecting the capacitive element to the threshold signal producing circuit in response to a switching signal and a discharge control circuit connected to the capacitive element, for selectively discharging the effective capacitance independently of the input signal, in response to a discharge signal. Also disclosed is a switch array employing structure similar to the above.

Abstract: A touch sensitive pad consists of a number of electrical conductive pads (10) surrounded by a conductive pad (11). Each pad (10) is connected via a respective capacitive blocking filter to a multiplexer (13) and an oscillator (14). When the touch pad is touched directly to effectively bridge between one of the pads (10) and the surrounding pad (11), a change in effective impedance is detected by a resultant variation in the frequency of the oscillator (14).

Abstract: According to this invention, a keyboard is constituted by 15 keys, and 4-bit data is sent to a keyboard controller in response to depression of a key. The keyboard controller detects the permutation of two continuously depressed keys. A key code is picked on the basis of the permutation with reference to a table stored in advance, and is sent to a system main body. The keyboard controller updates the table to another table in response to depression of a specific key.

Abstract: A data processor (50) includes a hardware keyscan circuit (54) to interface to an external keypad matrix (80). In one embodiment, the data processor (50) has a first register (62) for driving data to rows of the keypad matrix (80), and a second register (63) for inputting signals from columns of the keypad matrix (80). A set of weak pullup elements (71) connected to the columns is always conductive. A set of strong pullup elements (75) connected to the columns is conductive only after the hardware keyscan circuit (54) detects that a key (89) is depressed and disables the driving of the rows. Thus, pullup time and power consumption are minimized. The hardware keyscan circuit (54) also includes a data direction register (61) which has a shift control input terminal so that in response to a local state machine (64), the data direction register (61) acts as a shift register to sense the row with the depressed key (89), without intervention from a central processing unit (51).

Abstract: Disclosed is a scanning circuit for an electrical matrix keyboard. The keyboard has extended keys on a voltage line and a ground line. Two extended line detector are incorporated into the circuit for detecting the extended keys without increasing input and output ports of the circuit, so that the circuit can be integrated into a chip at a lower cost.

Abstract: A logic device having a state machine for serially transferring data between an AT-compatible mother board and a keyboard having a microcontroller for scanning the keyboard matrix, without the need for a microcontroller on the mother board. A timer is provided to signal a transmission time-out error, and to indicate the start delay before beginning to transfer data when transmitting to the keyboard. Transmission to the keyboard begins by asserting the clock and serial data bit to the keyboard, and waiting for the start delay to expire. The state machine has a chain of 22 states for transferring an 11-bit data frame, the state transitions occurring after the clock from the keyboard or mouse changes polarity. A time-out error state is entered if a timer indicates that a 32 ms period of time has elapsed. Both transmit and receive operations may time-out with the same delay, and enter the same error state.

Abstract: The REAL TIME KEYBOARD SCANNER shown herein provides scanning and debouncing, but not multiple key resolution or buffering. At the end of each keyboard scan, the scanner produces a code indicating which key was depressed, or that no key was depressed, or that multiple keys were depressed. If this code is the same as the code in a valid-key register, then no change is made to the valid-key register and no debouncing is performed. If the codes differ, then debouncing is performed. The CPU served by the scanner can examine the code in the valid-key register whenever it finds such examination to be convenient, and need not tie up valuable processing time in continuously monitoring the valid-key register. If desired, an interrupt may be sent to the CPU when the code in the valid-key register is changed.

Abstract: An input device, which utilizes a virtual keyboard, includes a device for designating at least one input-position in a virtual keyboard displayed on a display; an input-symbol defining device for defining a form and a meaning of each input-symbol drawn by the designating means (e.g., a write-pen); and a symbol recognition device for discriminating the input-position and related input-symbol drawn at the input-position on the basis of information defined by the input-symbol defining means. The input device generates a specified input-code in a real keyboard in accordance with a combination of the input-position and the input-symbol, and displays characters or symbols corresponding to the input-code on the display means. Preferably, the form of each input-symbol includes a length of a segment drawn by the designating device and a direction in which the segment extends.

Abstract: A computer keyboard having an output port through which scan codes are directed to a computer CPU over a cable, the keyboard of the kind having a touch activated membrane switch onto which one of a plurality of key layout overlays can be installed. Each of a plurality of different stored data tables is operable when selected to determine the particular scan code that is directed through the keyboard output port over the cable in response to a membrane switch being activated. Each overlay being coded in a way that can be read by an overlay code identification device which automatically operates in response to a coded key layout overlay being installed onto the keyboard to read the overlay code, which is then used by a data table selector to select a particular data table for use with the installed overlay.

Abstract: A keyboard interface controller in the nature of a state machine is placed in a stop mode or an idle mode after initialization. In stop or idle mode, all the keyboard conductors associated with the X-axis are activated, while all keyboard conductors associated with the Y-axis are sensed. Upon being awakened by an interrupt upon key closure from which the Y-axis location of the closed key is determined, the controller sequences through the steps of (a) determining the X-axis of the keyboard by activating the determined Y-axis conductor and sensing the X-axis conductors; (b) converting the crosspoint to a unique code; (c) transmitting the crosspoint code to the host; and (d) checking for either another closure or the release of the closure detected. When all keys are released, the controller returns to stop or idle mode.

Abstract: An N-key rollover circuit including a matrix of crossing drive and output lines, switch elements connected between the drive and output lines, series resistors connected to the switch elements and current detectors connected to the output lines. A grounded current detection resistor is connected to an input terminal of each current detector, each current detection resistor having a resistance value which is smaller than the resistance value of the series resistors such that most of the drive transmitted through a selected switch element onto an output line passes through the current detection resistor, even if more than one switch element is selected.

Abstract: A circuit has two multiplier modules. Each multiplier module has at least one controllable potentiometer for adjusting the amplitude ratio between an output signal and an input signal of the module. The potentiometers have substantially identical characteristics and they are controlled in the same manner such that the amplitude ratios of the multiplier modules are substantially equal. One of the modules receives as its input signal the first signal to be multiplied and delivers an output signal that is proportional to the product of the two operands, while the other module receives as its input signal a reference voltage and as its output signal it delivers a feedback signal which is servo-controlled to a value that is approximately equal to the value of the second signal to be multiplied. The circuit is applicable to meters for electrical energy.

Abstract: A switch matrix circuit is described that facilitates unambiguous detection of all two key selections in a scanned matrix of switches without requiring diode based isolation of the switches, software based interpretation or timing delays. The switch matrix circuit is applicable to keypads and the like and includes a matrix of switches arranged in a plurality of electrically connected rows and columns. Each row has a driver that is capable of selectively outputting a high impedance state and an active state. Each row also has a row sense amplifier for detecting the state of its associated row. Similarly, each column has a column sense amplifier for detecting the state of its associated column.

Abstract: A method differentiates simultaneous and sequential key strokes by detecting simultaneous key strokes if two keys are pushed within a judging time T.sub.L. The method includes the steps of (a) measuring a first time T.sub.1 from a time when a first key is pushed to a time when a second key is pushed, and a second time T.sub.2 from the time when the second key is pushed to a time when one of the first and second keys is released, (b) comparing the first and second times T.sub.1 and T.sub.2 with an arbitrary threshold function T.sub.C which is set within the judging time T.sub.L, and (c) differentiating whether key strokes of the first and second keys are simultaneous or sequential based on a comparison result of the step (b).

Abstract: A device for detecting switch closure such as in a keypad for entering data comprising a matrix of conductor pairs and switches, each pair of conductors shorted by the pressing of a particular switch, and current-regulating devices on each conductor for limiting current in one direction and passing it without limit in the other direction. The device is driven by alternating current. The ends of the conductors in a conductor pair limit current of opposing polarities with respect to each other so that the signal on a shorted pair is an alternating current signal with a unique combination of a positive and a negative peak, which, when analyzed, allows the determination of which key was pressed. The binary identification of the pressed key is passed to the input port of a host device.

Abstract: Information representing the state of switches carried on a pointing device handle is carried to an associated computer via a capacitive coupling technique.