Abstract: A printed wiring card tab protector for shielding the gold plated printed wiring card tabs from contamination with solder during a wave soldering process. The protector has a first fold that slips over the tabs and is thereby frictionally held in place while a second fold deflects away the solder wave.

Abstract: An arrangement for automatically testing a plurality of subscriber lines, which are operationally connected to an electromechanical switching system is shown. Operational service is to be transferred from the electromechanical switching system to a digital switching system. This arrangement provides for automatically verifying whether the digital switching system is applying the proper ringing signal to each subscriber by a comparison with that applied by the electromechanical switching system.

Abstract: An electrical to acoustic transducer utilizing the piezoelectric qualities of a polymer lamina and an arrangement including an amplifier and network to compensate for the polymer variability. This is accomplished by first providing two sets of electrodes on the surfaces of the polymer, a first set for driving the polymer and a second set for sensing the polymer electrical output and utilizing it via a compensating network operative to produce an output which is the square root of the products of inputs from the two sets of electrodes to precisely alter the amplifiers drive into the polymers first set to thereby maintain a desired constant acoustic output.

Abstract: A system for distributing signals from an audio source to key telephone station instruments is disclosed. By controlling the impedance relationship between the station instruments, lines and amplifier output, cross-feeding of signals from one station instrument to another or back-feeding of signals to the audio source is prevented.

Abstract: An arrangement for providing a subscriber line with an operating potential. The energy to the line is transferred thereto inductively at a fixed frequency and includes the rectification means on the subscriber side of the inductor. The amount of energy transferred to the line is controlled by pulse width. The control pulse width circuit includes means to decrease the energy transfer above a level at which a subscriber station internal regulation would be defeated.

Abstract: A circuit board positioning arrangement for multiple of circuit boards. Support apparatus maintains the circuit boards in a spaced parallel relationship while permitting movement of one board relative to another. Sequencing apparatus fixed to one of the boards engages receiving apparatus on another, positioning one of the boards forward of another. When force is applied to the least advanced board, the most advanced board engages an associated connector. Continued application of force then causes the sequencing apparatus to release allowing the next most advanced board to engage its connector.

Abstract: A "call-for-service" and continuity sensor circuit for use with a trunk circuit of a digital PABX telephone system interfacing with a central office via ground start signaling providing for detection of a "call-for-service" signal to the PABX by the central office. This circuit also provides high and closely matched tip to ground and ring to ground impedances for all trunk conditions in order to prevent excess loading of the trunk circuit. This circuit provides a precise and stable threshold detection level necessary for accurate sensing of the trunk circuit conditions mentioned above despite parasitic leakage current, induced longitudinal power line voltages, and earth potentials sometimes found to exist on the line connecting the central office to the PABX.

Abstract: A protecting arrangement is dislcosed for multiple loads supplied from a single DC power source. Each load is monitored by a separate protection circuit. Detection of an over-current condition associated with one of the loads will cause the associated protection circuit to assume a non-conducting state and provide a visual indication of same. Periodically enabled common reset means are provided to restore conduction to non-conducting protection circuits following removal of the cause of over-current.

Abstract: An improved selector card assembly for use in a paystation coin handling mechanism wherein the polarizing magnet normally molded into the end of the card is mounted onto the card by a pair of tines and a central saddle like tongue portion. Thus leaving the polarizing magnets poles exposed and closer to the coin magnet core extensions.

Abstract: A circuit for simulating the effects of a temperature change in a digital transmission medium. The circuit generates lengthened or shortened frequency pulses digitally by operating a pulse counter to reset early for a shortened pulse or skip a timing pulse for a lengthened interval pulse. A second counter and associated decoder are utilized to alternately control the operating modes.

Abstract: A circuit arrangement for comparing a clock pulse train against a standard pulse train. The circuit includes an exclusive OR gate to which are inputted the pulse train to be tested, and a latch at the output of the gate, operated only upon a mismatch of the two pulse trains. Provision is also made to prevent operation of the latch within certain adjustable tolerance parameters as to pulse width and position of the pulse train.

Abstract: An active circuit for modeling desireable diode and varistor characteristics in signal limiting circuits. The circuit includes a resistor arrangement for setting the desireable threshold voltage to an operational amplifier, the other input of which is connected to a reference voltage level. The amplifier output is tied back to the circuit input and to one input of a second amplifier. A second input is connected to the reference voltage level to act as a current sensor to vary the threshold level in response to the current flow.

Abstract: An apparatus adapted to check for the continuous presence of an incoming clock pulse train comprising an exclusive OR gate, to the input of which are coupled the clock pulse train and a second train of clock pulses delayed by one half the period of the incoming clock pulse train. A third train of clock pulses delayed by three quarters of the clock period is utilized to strobe the OR gate output into a pair of flip-flops. If the two inputs to the OR gate are the same a fault exists and a flip-flop is set to indicate on which excursion the fault occurred.

Abstract: A telephone call waiting signal system as used in a processor controlled exchange, wherein reuse is made of an existing ringing supply bus and the signal relay in each subscriber's line equipment for applying a call waiting signal to the subscriber's line. This is made possible by the multiplexing of the two signals and selectively operating the signal relay at the line equipment.

Abstract: An improved conference circuit for use in a Pulse Code Modulation telephone switching system wherein a number of channels are combined so that a number of subscribers may participate in a common telephone conversation. The conference circuit is provided with a voice level coding arrangement whereby the voice level comparisons used in the speaker selection process are facilitated, and with a multi-frame coded voice level summing arrangement whereby channel switching caused by spurious noise peaks is effectively eliminated.

Abstract: An improved conference circuit for use in a Pulse Code Modulation telephone switching system wherein a number of channels are combined so that a number of subscribers may participate in a common telephone conversation. The conference circuit is provided with a multi-frame voice level summing arrangement whereby spurious channel switching caused by noise peaks is effectively eliminated.

Abstract: An improved conference circuit for use in a Pulse Code Modulation telephone switching system wherein a number of channels are combined so that a number of subscribers may participate in a common telephone conversation. The conference circuit is provided with a voice level coding arrangement whereby the voice level comparisons used in the speaker selection process are facilitated.

Abstract: An interlock circuit is set forth which provides for controlling asynchronous data transfers between a host processor and a plurality of microprocessors via a common buffer. The interlock circuit consists of an interconnection of latches arranged so that the first processor initiating a transfer request inhibits all remaining processors from activating their respective transfer requests. Each processor upon terminating a data transfer clears its associated transfer request. The host processor can clear all transfer requests upon command.

Abstract: A device for the remote turn on of a teletypewriter of a distant terminal, such as at a hotel or motel. The turn on circuit is connected to the communication line to operate a magnetically latching relay. The latching relay operates to turn on the alternating current motor. The relay remains in its operated position until turned off by the end of message detector.

Abstract: Groups of analog trunks are shown connected to analog to digital converters. The converters are each assigned a time during which their associated trunks may access a common data bus to the pulse code time division switching system. Provision is made for the use of T1 carrier channels to utilize the times normally assigned for the analog trunks by the provision of a circuit that one excludes the other from accessing the bus.