Abstract: A space and time switch receives digitized voice and/or data as forty-six separate serial bit streams with each voice or data path occupying one time-slot on one bus, resulting in a total of 1472 paths entering the switch. The switch originates buses and the information in any incoming path can be switched to any outgoing path providing a 1472-by-1472 switching function. The switch includes six basic functional blocks: input, output, speech RAMs, control RAM, controller interface, and state machine. The controller interface receives commands in the form of twenty-four bits appearing as three bytes in three separate operations, stores the bytes until all three are ready, and transfers the command bytes as a combination of address and data bits. The speech RAMs store a complete frame of the data transferred within each time-slot. The control RAM stores commands from the controller interface.

Abstract: A telephone system that is useful for facilitating both voice and data communications uses an analog gate. An incoming data signal periodically enters the analog gate. A signal processing means receives the incoming data signal from the gate and an outgoing data signal turns off the gate. The signal processing means includes an automatic gain control for controlling the amplitude of the incoming data signal. The outgoing data signal turns off the gate preventing the outgoing signal from affecting the automatic gain control.

Abstract: A space and time switch receives digitized voice and/or data as twenty-two separate serial bit streams with each voice or data path occupying one time-slot on one bus, resulting in a total of 704 paths entering the switch. The switch originates twenty-two buses and the information in any incoming path can be switched to any outgoing path providing a 704-by-704 switching function. The switch includes six basic functional blocks: input, output, speech RAM, control RAM, controller interface, and state machine. The controller interface receives commands in the form of twenty-four bits appearing as three bytes in three separate operations, stores the bytes until all three are ready, and transfers the command bytes as a combination of address and data bits. The speech RAM stores a complete frame of the data transferred within each time-slot. The control RAM stores commands from the controller interface.

Abstract: A PCM rate conversion module is provided for interfacing a thirty-two channel PBX with a twenty-four channel link. The PCM conversion circuitry includes an inbound data memory station and an outbound data memory station wherein inbound T1 data is looped back out to the T1 data link and outbound PBX data is looped back out to the PBX. The looping provides effective and reliable testing of the rate conversion apparatus.

Abstract: A conferencing bridge is provided for an electronic telephone system to support telephone conversations involving three or more parties. The conferencing bridge implements a conferencing algorithm using simple arithmetic operations. The conferencing bridge circuitry implements the algorithm by summing each party's contribution to the conference deriving a grand total, and subtracting each party's contribution from the grand total.

Abstract: An improved time division multiplexed switch, particularly useful in a private branch telephone exchange. Any number of ports, limited only by the drive capability of the devices used, may be connected to the switch. Each port may transmit or receive on any combination of data line and time slot. Each combination of time slot and data line comprises a path, the number of paths being equal to the product of the number of data lines and time slots. Connection between a transmit port and receive port is implemented by writing a path select control word consisting of a time slot select control word and a data line control word to registers associated with the port. The register for the data line select on the receive side latches the data line select command into the select inputs of a multiplexer connecting the port receive line to the appropriate one of a plurality of data lines shared by the ports.

Abstract: A bistable switch for controlling a latching relay for connecting and disconnecting an air conditioning load, operable over a telephone line by the application of a short burst of one of a pair of determined frequencies. The switch includes a power supply capacitor (35) charged directly from the telephone line (32, 33). A pair of narrow band filters (39, 40) each respond to one of the pair of frequencies. The output of each filter drives an FET amplifier (60) which in turn drives a charge pump (68, 69). When a sufficient amount of charge is received, the charge pump will provide a firing pulse to one of a pair of SCRs (77). The SCRs are each connected in one leg of a bridge circuit which includes one of a pair of diodes (79). The remaining legs of the bridge are formed by a pair of transistors (80) with the coil (46) of a bistable relay (47) attached across the bridge.

Abstract: A multiplexed liquid crystal display arrangement including a back plane (241) driven by a signal (212) derived from a common clock signal (200). The clock signal on the back plane is also provided to one input of an EXCLUSIVE OR gate (245b) the other input of which is the incoming multiplexed data. A second clock signal (211) drives the multiplexing counter (141) which in turn drives the address lines (221) of an analog multiplexer (138). Each segment of a multi-segment liquid crystal display having the common back plane (241) has attached thereto a capacitor (C1 through C64) acting as a temporary storage for the signals. A spike suppression flip-flop (247) is used to disable the multiplexer during changes on the address lines in order to suppress output spikes which occur during such changes. The period of the spike suppression pulse is selected to be short with respect to the on period of each segment in the multiplex timing.

Abstract: An interface for connecting a PBX line (18) to a central office trunk (15) and for providing a supervisory signal (28) and accepting PBX hook switch and dial pulse inputs (30), being readily adaptable to ground start trunks and loop start trunks. A pair of transistor switches (55, 56) sharing a common base drive (57) is biased by a differential bias means (59, 60, 61) to operate a ground start isolated switch (32, 35) and an isolated loop closing switch (36, 37). The supervisory signal is controlled by a comparator (45) which senses grounding of central office tip (16) to establish the supervisory signal and is subsequently responsive only to the presence of current in the central office loop detected by a relay (65) buried in a coupling transformer.

Abstract: A data distribution system for a private branch telephone exchange for providing information to a plurality of PBX stations. Two embodiments (serial and parallel) including addressable stations are shown. Memory devices driving a plurality of displays at each station are updated in response to command signals from a controller preceded by the station address. Each station may communicate with the controller and transmit keyed-in signals or information reflecting station availability. A novel multiplexed LCD, switching matrix bypass upon controller failure circuit, and bus protection circuit upon remote power supply failure are also shown.

Abstract: A private automatic branch telephone exchange system which includes an integral system for maintaining and updating selected data information. Interconnections between subscriber lines and trunk lines are accomplished with a unique non-blocking switching matrix which allows switching interconnections to be independently made and terminated without blocking subsequent interconnections on the same circuits. Various information signal functions, such as dial tone and ring-back, are selected by multiplex circuitry which is external of the switching matrix, so that all switching matrix trunks are available for voice and ring signal connections. The switching matrix is operated by a circuitry including a programmed digital computer, and provides substantial flexibility of control and service functions. Subscriber line status is monitored at all times, so that available special services can be accomplished by a subscriber in response to dialing selected digits.