Abstract: Presently available printed wiring board backplanes used in switching systems and the like are wired at the time of manufacture to enable only a fixed number of groups of circuit boards to communicate with each other. This limitation prevents a backplane from having the capability of serving a varying number of groups of boards. The present invention enables a backplane to have the capability of serving a variable number of groups of boards. The number of groups that can be served by a given backplane need not be fixed when the backplane is designed and manufactured. Each backplane of the present invention comprises backplane bus conductors and board conductors. The boards are effectively a part of the bus. The use of a first type of board in a backplane connector continues the bus to the adjacent connector. The use of a second type of board terminates the bus and does not extend it beyond the connector into which the second type of board is inserted.

Abstract: Circular paths in a multinode connection are avoided by passing an adaptive routing state, from node to node, which specifies the path options that the current node may use in its selection of a next step in the connection. The routing state, which is characterized by, for example, a single digit, is updated by the current node and is a function of the recent path history of the connection. The single-digit routing state controls the advancement of the connection by specifying whether the next selected step can be either a forward step, a null step or a backward step, or any combination thereof. A forward step advances the connection toward its destination, a null step does not advance the connection and a backward step causes the connection to step backward to a node not yet in the connected path. When a node selects a next step, it adapts the routing state digit to reflect its selection and passes the new routing state digit to the next node.

Abstract: A receiver circuit uses switched capacitor circuits to couple signals received over a communication facility to connected apparatus. During a first time interval a capacitor is connected across each lead of a facility to sample the facility voltages. During a second time interval these capacitors are disconnected from the facility lines and reconnected in series as the input to a voltage regenerator circuit. The regenerator circuit reconstructs the received signals for output to connected apparatus.

Abstract: A packet switching system having separate arbitration and data buses together with circuitry for dividing the buses into a plurality of time segments termed phases. The plurality of phases permit a like plurality of separate arbitration operations and a like plurality of separate data exchanges to be effected concurrently on the arbitration bus and data bus, respectively. The use of n phases increases the data transmission capability of the system by a factor of n over prior art arrangements using only a single phase.

Abstract: A jack has therein a longitudinal guideway in the back of which the free end of a printed wiring jack board projects longitudinally forward in the guideway and has laterally spaced conductive terminals on its top. The guideway is adapted to slidably receive a cartridge connector plug comprising a cartridge housing with a front opening for a longitudinal passage therein, a pair of axleless resiliently deformable lateral rollers in said housing back of said opening on opposite sides of said passage, and a flex bond unit longitudinally displaceably received in the passage and comprising a printed circuit plug board and a flexible sheet bonded to that board and having a forwardly projecting tail with laterally spaced conductive terminals matching those of the jack board.

Abstract: An arrangement for achieving multi-processing is disclosed for use in a communication system where it is desired to have several independent processors operating in parallel on stimuli received from the connected terminals. Each such terminal is associated with a particular processor and that processor serves to control connections involving its associated stations. Stimuli from the station are stored in a queue and processed in an intermixed fashion such that stimuli from the connection are processed in order of arrival of the stimulus, but stimuli from different connections are processed without regard to the relative order of arrival of stimuli between connections.

Abstract: The adjunct call processing arrangement of our invention eliminates the separation between hard-wired telephone switching system computer facilities and customer owned switchably connectable computer facilities. A general purpose communication interface is provided which connects the customer provided computer facilities to both the switching network and the hard-wired system processor of the telephone switching system via the standard telephone switching system port circuit. This general purpose communication interface enables a customer provided computer facility to provide additional call processing capability. In particular, the attendant services call processing subroutines and the directory assistance data base and software are provided on the computer facility. The telephone switching system routes all attendant-directed calls to a telephone station set associated with the computer and transmits call related data to the computer.

Abstract: An FSK demodulator of the differential type is arranged to provide two versions of an input FSK signal that, relative each other, (1) have a linear phase shift versus frequency characteristic and (2) are phase shifted by 90 degrees at a center frequency halfway between the upper and lower FSK frequencies. The linear phase shift is provided by an N sample delay element, while a constant phase shift circuit which includes a K factor gain element provides the 90 degree phase shift. By virtue of this arrangement, the demodulator characteristics can be adaptively varied and the demodulator tuned simply by changing the value of K. A similar adaptive technique is applied to a threshold detector arranged to position a threshold midway between the extremes of an input signal.

Abstract: This invention relates to line circuits and, in particular, to the apparatus contained therein for switching the ringing signal on to the communication pair which connects the line circuit to the telephone station set which it serves.Electromechanical relays provide an ideal switching function but require a significant amount of space while semiconductor switches do not require much space but provide an imperfect switching function which adversely affects the performance characteristics of the line circuit.The subject ringing apparatus makes use of a semiconductor switch to provide the ring relay function and incorporates additional circuitry to eliminate the difficulties associated with semiconductor switches.

Abstract: Synchronization facilities are disclosed for maintaining error free timing of a digital system when control of the system timing is switched between a plurality of clock sources. The signal of each source is applied to an associated counter divider whose output is applied to switch facilities which extend the output of only one divider at a time as a reference clock source to the digital system. The dividers for the other sources are forcibly reset each time the divider of the reference source advances from its all 1s to its reset (all 0s) position. This maintains the output signals of all dividers in phase with each other to prevent disturbances to the digital system when its timing is switched between clock sources.

Abstract: In a system for communicating primary and secondary data from a transmitter to a receiver, each of a first plurality of primary data word values is communicated by the transmitter by transmitting an individual channel symbol associated with that value, while each of at least two other primary data word values are communicated by transmitting a selected one of at least two other channel symbols associated with that primary data word value. A predetermined one of the two channel symbols associated with the first primary data word value is transmitted only when secondary data having a first value is to be communicated, and a predetermined one of the two channel symbols associated with the second primary data word value is transmitted only when secondary data having a second value is to be communicated. In the receiver, both the primary and secondary data word values are recovered from the channel symbols thus transmitted.

Abstract: A receiver circuit uses a switched capacitor circuit to couple either analog or digital signals received over a two lead communication facility to connected apparatus. During a first time interval, a capacitor is connected across a lead of a facility to sample the facility voltage. During a second time interval, this capacitor is disconnected from that lead and reconnected in series between the second facility lead and the input to a voltage regenerator circuit. An appropriate regenerator circuit is selected to reconstruct either the received analog or digital signals for output to connected apparatus.

Abstract: A modular plug connector is adapted to terminate a cord having a number of insulated solid wire conductors. The connector includes a dielectric housing that facilitates interconnection between the solid wire conductor and a metallic terminal which slides into a terminal-receiving slot of the dielectric housing. The metallic terminal includes three tangs, or blades, that pierce the insulation surrounding the solid wire and achieve electrical contact. Adjacent tangs grasp the solid wire on opposite sides of its center line, but are controllably spread before making contact with the wire by cam surfaces molded into the side walls of the terminal-receiving slot. Reliable connections are therefore made between a metallic terminal and a solid wire conductor without severing it.

Abstract: This circuit uses a simple structure of series-parallel connected capacitors and diodes to implement an n/m voltage divider circuit. There are n columns of series connected capacitors, which columns are all connected in parallel. The capacitor valves are selected so that in each column the ratio of charging capacitance to discharging capacitance is n:m. The diodes automatically switch the capacitor charging and discharging currents to the series-parallel connected capacitors.

Abstract: A ringing signal reformatting circuit detects ringing signals having one or more ringing bursts and generates a code representing a modified distinctive ringing signal having a predetermined number of bursts and a predetermined on/off timing in response to all detected ringing signals having the same number of ringing bursts. This coded ring signal is sent to a station set and decoded thereat to generate a distinctive ring signal.

Abstract: This integrated message service system provides a user with an indication of which of a plurality of message service systems contain unretrieved messages. This is accomplished by the serving telephone switching system maintaining a translation memory that indicates both the type of message services assigned to each user and the location of unretrieved messages in the assigned message services. The translation memory is updated every time a user creates a new message or accesses a previously stored message.

Abstract: A trunk circuit interfaces a multichannel data signal to a communication facility using a high priority queue (HPQ) memory, a low priority queue (LPQ) memory, and a data packet sorter including a separate LPQ counter for each data channel. Each LPQ channel counter keeps track of data packets from the associated channel which are stored in the LPQ memory. The packet sorter sorts data packets according to size. Small data packets from each channel which are smaller than a predetermined length are sorted for storage in the HPQ memory only when the associated LPQ channel counter is zero. Small data packets having a non-zero LPQ channel count and large data packets are stored in the LPQ memory. The trunk circuit first transmits data packets from the HPQ memory and then from the LPQ memory.

Abstract: In a system for communicating primary and secondary data from a transmitter to a receiver, each of a first plurality of primary data word values is communicated by transmitting an individual channel symbol associated with that value, while at least one other primary data word value is communicated by transmitting a selected one of at least two other channel symbols associated with that one other value. The selected symbol is a function of the value of an individual secondary data word. In the receiver, both the primary and secondary data word values are recovered from the channel symbols thus transmitted.

Abstract: In a cryptographic communication system, a first encryptor transmits to a first decryptor and a second encryptor, co-located with the first decryptor, transmits to a second decryptor, which is co-located with the first encryptor. Each encryptor/decryptor pair is adapted to communicate using a selected non-self-synchronizing cryptographic mode. Whenever it is determined that synchronization between, say, the first encryptor and the first decryptor has been lost, both the first decryptor and the co-located, second encryptor are switched from the non-self-synchronizing mode to the self-synchronizing mode. This causes a loss of synchronization between the second encryptor and second decryptor since the latter is still operating in the non-self-synchronizing mode. Upon detection of this loss of synchronization, the second decryptor and the co-located, first encryptor are also switched from the non-self-synchronizing mode to the self-synchronizing mode.

Abstract: A self-oscillating switching regulator includes an inductor which is switched across the input or output depending, respectively, on whether a control voltage does not or does exceed a predetermined threshold. The control voltage is generated from a predetermined sum of the output voltage and a voltage dependent upon the inductor current when the inductor is connected across the input.