Abstract: A telephony network with a digital central office and one or more remotely located digital satellite units. Each digital satellite unit connects to a number of remote subscriber lines and monitors these lines to establish communications through interconnecting spans and a digital satellite interface at the digital central office. The digital satellite interface also connects to port group highways in the digital central switch, to call processors in the digital central switch, and to a maintenance processor in the digital central switch. An automatic test circuit communicates with the interface, and each remote digital satellite unit contains complementary testing circuitry. A test call is made to test the system by activating a test access relay at the remote digital satellite unit and producing a call to the automatic test circuit. The automatic test circuit then generates a tone that is carried as voice data to the remote digital satellite unit test circuit.

Abstract: A telephony network with a digital central office and one or more remotely located digital satellite units. Each digital satellite unit connects to a number of remote subscriber lines and monitors these lines to establish communications through interconnecting spans and a digital satellite interface at the digital central office. The digital satellite interface includes a programmed controller that communicates with the remote digital satellite units connected to it, with call processing equipment in the digital central office and with maintenance processing equipment in the digital central office. Supervisory information and voice data information, in digital form, pass through span equipment that interconnects port group highways in the digital central office and the interconnecting spans. The span equipment strips messages from and inserts messages into signalling time slots on the interconnecting span.

Abstract: A telephony network with a digital central office and a one or more remotely located digital satellite units. Each digital satellite unit connects to a number of remote subscriber lines and monitors these lines to establish communications through interconnecting spans and a digital satellite interface at the digital central office. The digital satellite interface includes a programmed controller that communicates with the remote digital satellite units connected to it, with call processing equipment in the digital central office and with maintenance processing equipment in the digital central office. Communications with the maintenance processor are in the form of messages having a header byte and a byte indicating the length of the message. During network initialization and various recovery operations, the programs and/or the data base can be transferred from the maintenance processor to each digital satellite interface through the use of these messages.

Abstract: A community office switching system includes a three-level hierarchy of distributed processors operating in parallel with one another to control the operation of a central office matrix switch network interconnecting 1,920 ports. At the highest level, a stored-program call control processor controls call progression, establishing paths through the matrix switch network. At the second level, a series of special-purpose, stored-program, port control processors each service 960 ports, sensing and transmitting supervisory signals and communicating the occurrence of significant port events to the call control processor. Each port event control processor dedicates approximately 32 microseconds out of every 32 milliseconds to each of the 960 ports in time-multiplexed fashion, and hence no port can ever be locked out at the port-control-processor level. One from a series of stored programs is executed to service each port precisely one every 32 milliseconds.

Abstract: A telephony system with automatic test calling. Test access circuitry connected to port circuits enables the test call circuit to select actual ports for a test call and monitor the test call signals. Test calls are initiated either on a periodic basis on in resonse to a fault condition. Any portion of the telephony system therefore can be used in a test call.

Abstract: A private telephone network that includes multifunction telephones. Multifunction telephones are connected to common equipment by a voice signal path and a data signal path. Supervisory information passes over the data signal path in the form of polled messages that are sent from the common equipment to the telephone. Sense information is received by the common equipment from the telephone. The transmission is by frequency modulation, such as frequency-shift-keying modulation, techniques. At the multifunction telephone, a programmed microcomputer contains three blocks of instructions for enabling the microcomputer to perform background operations, to respond to the initial receipt of a message, and to thereafter transmit and decode the message. Further, in response to the decoding block of instructions, that are provided on a fixed time basis, the microcomputer is able to transmit frequency-shift-keyed signals without the need for a separate frequency-shift-keyed transmitter.

Abstract: An electronic telephone employing transmit and receive solid-state amplifiers having sufficiently low DC resistance to be biased by a DC signal over a pair of conductors with substantially less than four volts and having sufficiently high AC impedance for transmitting AC communication signals over and receiving AC communications from that pair of conductors. The amplifiers are directly coupled to the conductors, and the amplifiers include a transmitter section comprising a microphone and first solid state amplifier coupling the microphone to the pair of conductors, and a receiver section comprising a speaker and a solid state amplifier coupling the speaker to the pair of conductors. A shunt circuit is connected across the pair of conductors to adjust impedance characteristics of the telephone responsive to the available DC bias.

Abstract: A remote unit contains function circuits to be controlled in response to control data from a central location and function circuits to generate information for transfer to the central location. The control data is transferred between the remote unit and the central location as frequency-shift-keyed signals. In the remote unit, a programmed microcomputer contains three blocks of instructions for enabling the microcomputer to perform background operations, to respond to the initial receipt of a message, and to thereafter transmit and decode the message. Further, in response to the decoding block of instructions, that are provided on a fixed time basis, the microcomputer is able to transmit frequency-shift-keyed signals without the need for a separate frequency-shift-keyed transmitter.Table of ContentsCross References to Related Patent ApplicationsBackground of the InventionSummaryBrief Description of the DrawingsDescription of an Illustrative EmbodimentA. General DescriptionB. Specific Description1.

Abstract: A private telephone network that includes multifunction telephones. Multifunction telephones are connected to common equipment by a voice signal path and a data signal path. Supervisory information passes over the data signal path in the form of polled messages that are sent from the common equipment to the telephone. Sense information is received by the common equipment from the telephone. The transmission is by frequency modulation, such as frequency-shift-keying modulation, techniques. At the multifunction telephone, a programmed microcomputer contains three blocks of instructions for enabling the microcomputer to perform background operations, to respond to the initial receipt of a message, and to thereafter transmit and decode the message. Further, in response to the decoding block of instructions, that are provided on a fixed time basis, the microcomputer is able to transmit frequency-shift-keyed signals without the need for a separate frequency-shift-keyed transmitter.

Abstract: A fault monitoring and diagnostic system for a telephony switching system. Two call processing systems connect through a programmable switch to port group units that receive individual telephone lines. All signals from the port group units are conveyed to both call processing systems, and the call processing systems operate in synchronism. However, the programmable switch conveys signals back to the port group units from only one of the call processing systems. Fault monitoring and diagnostic circuitry monitors various conditions within the telephony switching system. A test call generator automatically performs test calls thereby to diagnose system problems. If a fault is detected, the fault monitoring and diagnostic system controls the programmable switch and, in appropriate circumstances, couples the output signals from the other call processing system to the port group units. Information concerning the nature of the fault is also provided.

Abstract: In a digital data transmission system including one or more matrix switches in which data in digital form is stored in a send memory during one selected time slot of a recurring time frame, transferred to a receive memory and sent out from the receive memory during another time slot of the recurring time frame to establish desired data paths through the switch between selected inputs and outputs, means is provided in the form of a programmable read only memory to control the insertion loss of each data path in a selective manner.

Abstract: An operator complex in which control signals relating to key lamp and alphanumeric display operation and key transition data are carried between the operator console and the PABX system on a multiplex highway or radio transmission link to permit virtually unlimited spacing between the operator console and the associated switching system. The operator console includes a send control system and a receive control system. The send control system detects valid key transitions and formulates a message concerning such detected key transmissions to be sent to the common control in the PABX. The receive control system receives messages from the common control indicating key lamp or alphanumeric display information and decodes these messages to effect selective control over the display.

Abstract: A digital conference circuit provides greater stability in voice transmission by selectively inverting the signal in alternate conference channels, thereby providing cancellation of parasitic echo signals which tend to create oscillations or ringing. Selective gain control is also provided for conferences of different sizes and efficient use of conference lines is ensured by providing for selective combination of conference groups.

Abstract: An electronic equivalent of an X-Y switch is provided using time division multiplex techniques. The basic switch includes a multiplexing section and a control section, the control section responding to signalling information received on the multiplex line including dialing impulses to determine each successive digit as it is dialed for controlling the steering of voice and signaling information through the multiplexing section to an output of the switch designated by the received digit on one of a plurality of free levels determined by a selected time slot. Thus, a switch having plural outputs with plural levels on each output electronically operates in the manner of the known X-Y switch but with reduced physical size and lower maintenance requirements.

Abstract: An air-fuel ratio control system for an internal combustion engine utilizes an oxygen sensor to maintain a 14.5/1 air-fuel ratio at a first location in an intake manifold to an engine combustion chamber. A method and apparatus is disclosed for adding fuel and/or air to the air-fuel mixture at a second location, between the first location and the engine combustion chamber, so that the engine operates at a high economy, low emission point when idling, running at a substantially constant speed or decelerating and operates at a low economy point, yet still with low emissions, only when accelerating.

Abstract: A unitized shelf and guide framework for supporting so-called printed circuit cards in spaced alignment. Open-work shelves are joined, for example by welding, in accurate alignment to corner posts to form a frame. Each shelf consists of longitudinal channel members extending in parallel array between end flanges, and may be formed by punch press of a single piece of metal. The channel members are covered by split sheathes, which may be molded of a plastic, and which carry transversely extending alignment bosses for guiding and positioning the circuit cards. A wired back plane of the usual kind is secured in predetermined alignment behind each shelf, and carries the usual receptors for the pin terminals that extend from the back edges of the cards.

Abstract: A levered inject-eject cam device is provided for pivotal mounting at the upper and lower corners of the rear edge of a printed wiring board. The cam is constructed of an integral molded body member having a bifurcated configuration which forms branching members which receive the wiring board therebetween. The branching members form flat stock members and the cam is formed as a profile shape of these flat stock members to engage a fixed engageable strip which extends toward the edges of the printed wiring board from the frame of the wiring board cell. A tyne is integrally molded into each branching member to resiliently grasp the board. The tynes provide sliding friction which permit the cams to be prepositioned before the wiring board is inserted into the cell so that the cams will be in proper position to cam the engageable strip, and not be in an undesired position in which the cam lobe strikes against the engageable strip and prevents insertion.

Abstract: Centralized toll restriction for private branch exchanges (PBXs) is performed by providing first and second memory addresses in the number translator of a central office switching system. The first and second addresses are matched with restricted telephone calls and unrestricted telephone calls, respectively. Those telephone lines of each PBX which are to be restricted are marked in a convenient manner, such as with tip to ground marking, while those telephone lines not restricted are left unmarked. Outgoing trunks between the PBXs and the central office switching system are temporarily marked with an unbalance upon going off-hook on a restricted telephone line, in order to transmit restriction indication to the central office switching system.