Abstract: A control transistor and a pnpn device are arranged in serial combination with each other, as well as with a source of alternating current and a load. The transistor and pnpn device in combination behave as a two-state semiconductor switch for switching cyclically varying currents and voltages of amplitude greater than the punch-through voltage limit of the transistor. The switch conducts an unrectified, cyclically varying waveform by operation of a diode biasing scheme. Circuitry responsive to voltage peaks of the source causes the transistor to periodically open the circuit for a short duration, thereby discontinuing the transmission of energy to the load within a fraction of a cycle after a discontinuation command signal is received.

Abstract: A data signal stream includes, in a noisy signal channel, periodic word synchronization characters, and each such stream is preceded by a burst of predetermined bit rate information. An approximate bit rate timing signal is derived from the data stream and utilized for producing an initialization pulse when the predetermined bit rate information is detected. In addition, the approximate bit rate timing signal drives a digital phase-locked loop which is preset by the initialization pulse to a digital circuit state defining operation at the nominal frequency of the approximate bit rate timing signal. A stable bit clock signal provided by the phase-locked loop controls the operation of further circuits which are responsive to the baseband data stream for providing an indicator pulse each time that a synchronizing character appears in the data stream.

Abstract: Signal transmission circuit characteristics are supplemented by a negative conductance circuit in which current sources of complementary polarity are connected in shunt between the conductors of the signal circuit. Changes in the voltage level of one side of the signal circuit are sensed at a point common to the two sources and applied through a positive impedance to control the current output magnitude of one of the sources for effecting a supplementing of the signal circuit current as though the changed voltage level had been applied in the presence of a negative form of that impedance connected at that common point.In additional embodiments, different, or variable, positive impedance are connected in the sensing circuit output coupling to cause the negative of such impedance to appear at such signal circuit terminal.

Abstract: In a radio communication system of the cellular type wherein sets of communication channels are reused in different adjacent sets of cell areas within a common mobile communication service area, each cell base station utilizing a given set of channels in common with other base stations is assigned a different supervisory tone to be modulated on all of its channels. Any mobile unit receiving such channel transponds the modulated supervisory tone and sends it back to the base station. At each base station the transmitted and received supervisory tones for any given channel are compared to produce an indication of whether or not the sending mobile unit is actually communicating on the transmitted channel of the same base station. At each mobile unit, reference tones are generated which are spectrally located between adjacent ones of the possible supervisory tones for the mobile communication area, and the spectral position of a received tone with respect to the reference tones is determined.

Abstract: A nonlocking key telephone station is arranged to display full line status information when the station is on-hook and for normally illuminating only the key lamp associated with the line in use at the station when the set is off-hook. To permit a user to discern the full status of the lines terminating at the set when the set is off-hook, circuitry responsive to the depression of one of the keys at the station is provided for displaying full line status information.

Abstract: In a multitone pushbutton dial array each switch in the array has a variable impedance coupling between a fixedly mounted conductive plate and a movable conductive plate spaced apart from the fixedly mounted plate. Digitally synthesized signals having a predetermined phase and frequency are sequentially and recurrently used to scan interconnected columns of movable plates in the pushbutton dial array. Signals having an opposite phase from the scanning signals are continuously applied to the fixedly mounted plates. When a pushbutton is depressed variable impedance coupled summation signals are produced and these signals have a phase which is opposite to that of signals coupled to the detector from an unoperated switch. The detected digital signals are used to generate digital multitone row and column frequency signals. These digital row and column signals are converted to analog form and are transmitted to a telephone central office as a dialed digit code.

Abstract: A line interface unit for a digital local office for telephonic communication has a circuit connected to telemeter low-frequency signals around a line, alternating current, hybrid coupler and reinsert the same signals in the call path at the input to an analog-to-digital encoder that is coupled to a time division switching network. Each interface unit also includes circuits for multiplexing various line unit, digital, status signals with coded call signals and for demultiplexing line unit, digital, control signals from coded call signals. That network is utilized by an office common control for interconnecting various call paths with one another and for interconnecting the common control with the line interface units as required. The common control includes a time-shared digital filter for processing the telemetered signals for various office purposes.

Abstract: Digital character signals are split into at least two bit groups of different binary significance. The first and most significant of the bit groups is registered and periodically sampled for conversion in a resistor network to an analog format. The bits of the second, or least significant, bit group are utilized to produce a signal train including in a character time a number of pulses determined by the value of the second bit group and which pulses are approximately evenly located in the interval of the character. Each pulse of the train, as it occurs, momentarily augments the most significant bit group.One embodiment is shown in which the signal train produced is successive overflow carries from a high speed accumulation operation initially utilizing the least significant bit group and a starting character and thereafter using the least significant bit group and the immediately preceding accumulation sum.

Abstract: A self latching and unlatching connector assembly includes first and second connectors having mating electrical contacts. The first connector has affixed thereto a pair of latch members. The second connector is mounted in an assembly which includes upper and lower shell halves, each of which has a groove therein for engaging a mounting flange on the connector. A pair of levers, each having first and second arms, are mounted on a pair of pivots which are integral with the lower shell half. One arm of each of these levers engages one of a pair of spring latches, each of which has provision at one end thereof for latching the second connector assembly to the first connector latch members. A sleeve having a pair of locking pins affixed thereto fits over the two mated shell halves. To effect disconnection the sleeve is grasped at any position on its periphery and pulled.

Abstract: A line switch controller for time division telephone switching systems incorporates the function of a time slot assignment memory. Time slots are defined by the repetitive numerical sequence produced by a local time slot counter in enumerating clock pulses. Line switch closures effecting the connection of parties via a time division bus are performed in response to the attainment of a predetermined count in presettable control counters each dedicated to a different line switch and enumerating clock pulses up to the same maximum enumeration of the time slot counter. Repetitive closure of a line switch in a particular time slot is achieved by setting the corresponding control counter to the predetermined count in that time slot. Quick access to time slot assignment information is attained through the inclusion of a binary multibit subtractor to take the difference between the time slot counter enumeration and the enumeration of a selected control counter.