Abstract: An improved ringing generator is disclosed, for producing and transmitting an AC ringing voltage waveform to a subscriber line from a negative and positive DC voltage source. The ringing generator is characterized by a transformer having a primary winding and a secondary winding. The primary winding includes a plurality of taps dividing the primary winding into a plurality of winding segments. The secondary winding is connected to subscriber line via a filter network. Each winding segment is connected to a buffer-driver which has a first lead connected to the DC voltage source and a second lead connected to a source of control signals. Responsive to the control signals a selected pair of buffer-drivers are alternatively enabled connecting for a predetermined time period the associated coupling segments to the DC voltage source thereby, producing a switched ringing voltage waveform which is coupled to the secondary winding.

Abstract: A circuit providing a message waiting indication using a light emitting diode and a constant current surge protected circuit for use with PABX extension telephone instruments. Recently developed light emitting diodes operated with current of one milliampere or less are effectively used in the present circuitry which limits current to the device in the operating mode and also as low leakage current while in the "off" mode.

Abstract: A solid state circuit designed to be incorporated into a telephone terminal instrument to provide a visual indication at that instrument that a telephone line to which the instrument is connected is already in use by another telephone instrument.

Abstract: A module for cooling equipment mounted in a frame. The module includes a plenum positioned between an upper portion and a lower portion of electronic equipment and a panel positioned across the plenum to occlude it. The panel is of multiplanar arcuate construction including a first, a second and a third panel portion each provided with an aperture in which is mounted to a fan. A pair of vanes between adjacent fans are provided. The vanes align themselves with the air flow from adjacent fans when both adjacent fans are operational and position themselves across the aperture of an adjacent fan when failed.

Abstract: A circuit arrangement for use in telephone instruments which require battery backup for memory retention and microprocessor operation during such procedures as pulse dial address signalling where no power can be supplied by the telephone subscriber's line. Bipolar solid state circuitry may be used to provide the necessary backup power supply during these periods.

Abstract: A disconnect circuit for use between two switching systems. An optical coupler monitors open and closed current loop conditions and provides signals representative thereof. Monostable multivibrators are operated in response to these signals to provide timing signals of predetermined durations. A relay circuit is controlled by these timing signals and it operates to disconnect the loop between the switching systems for a predetermined time.

Abstract: This disclosure teaches a diagnostic method for finding faults in a unique addressing scheme. A telecommunications system controls external devices by operating control and sense point printed wiring cards. These printed wiring cards are organized to operate when selected by a processor. Two address components select the identity of a particular printed wiring card of a number of printed wiring cards to be operated. This invention detects any addressing apparatus which is permanently active, stuck to logic one. This method operates continuously to build a table of faulty equipment indications.

Abstract: Method and apparatus is disclosed for identifying faults in a subscriber carrier telephone system utilizing out-of-band pilot signals and comprising pluralities of cables and repeaters that are alternately connected in series between carrier equipment at a central office location and a subscriber station. Equipment at the office location transmits selected numbers of test pulses, having a test frequency that is between the transmitted and received channel and pilot frequencies, to the first cable. The pulses are detected at the first repeater and counted. A microprocessor is responsive to the test pulse count in the repeater for initiating associated tests on the cable and/or repeater, or for retransmitting test pulses onto the next cable to the next repeater for causing it to perform designated tests. The results of the tests are sent to the office equipment in the form of reply pulses having a frequency that is below the lowest channel frequency.

Abstract: An assembly to reduce propagation of electromagnetic interference from an equipment enclosure via cable conductors passing out of the enclosure including a capacitor connected to each corresponding conductor and to the enclosure. The capacitors are mounted on an insulating substrate to which is fixed a conductive layer. The capacitors, the support plate, and the conductive layer are contained in a housing attached to the equipment enclosure. A second enclosure is provided, received within the housing and is equipped with a pair of clamps to retain the cables connected to the capacitors from both outside of and within the equipment enclosure.

Abstract: A beam lead bonding apparatus for bonding simultaneously, a plurality of beam leads of varying thicknesses to bonding bumps of varying heights on an integrated circuit substrate subject to cracking when subjected to a predetermined bonding force. The substrate is supported on a base with beam leads in alignment with corresponding ones of the bonding bumps. A resilient pad is provided between the substrate and the base and compressed in response to unequal deflections of the substrate when a bonding element is moved in a direction towards the base to bond the beam leads to the bonding bumps. An alternate compliant pad is disclosed together with an alternate structure for distributing bonding energy throughout the bonding substrate and an alternate arrangement for preventing beam lead to substrate shorts.

Abstract: A multiple port serial link controller printed wiring card is shown. This printed wiring card provides at least two independent ports. These ports may be of different types such as RS-232 interface, RS-449 interface or other serial protocols such as HDLC, SDLC or BISYNC. These printed wiring cards may be combined in a duplex fasion to form two duplex (highly reliable) port transmission circuits. The duplex configuration requires a minimum amount of backplane wiring. This backplane wiring is permanent and requires no manual intervention for switching between transmission and mode types. Switching between transmission mode type and reconfiguring for the occurrence of faults may be accomplished by an automatic processor manipulation of a number of control points.

Abstract: A multiple port serial link controller printed wiring card is shown. This printed wiring card provides at least two independent ports. These ports may be of different types such as RS-232 interface, RS-499 interface or other serial protocols such as HDLC, SDLC or BISYNC. These printed wiring cards may be combined in a duplex fashion to form two duplex (highly reliable) port transmission circuits. The duplex configuration requires a minimum amount of backplane wiring. This backplane wiring is permanent and requires no manual intervention for switching between transmission and mode types. Switching between transmission mode type and reconfiguring for the occurrence of faults may be accomplished by an automatic processor manipulation of a number of control points.

Abstract: This disclosure teaches a diagnostic method for finding faults in a unique addressing scheme. A telecommunications system controls external devices by operating control and sense point printed wiring cards. These printed wiring cards are organized to operate when selected by a processor. Two address components select the identity of a particular printed wiring card of a number of printed wiring cards to be operated. This invention detects any addressing apparatus which is permanently inactive, stuck to zero. This method operates continuously to build a table of faulty equipment indications.

Abstract: A temperature compensated voltage reference circuit adapted for on chip location with integrated bi-polar linear circuits, where a temperature stable reference voltage is required in the range of 1.2 to 2.0 volts DC. The circuitry requires only a low chip area and presents a high AC impedance, a low operating current drain, and requires no high value resistors or capacitors.

Abstract: A fast response electronic switch used for control of connect and disconnect functions, primarily related to speech network applications for electronic-microprocessor based telephones utilizing dual tone multifrequency and/or universal pulse dial address signaling. Disclosed circuitry includes an active surge protector, a saturated transistor switch and bias circuit which exhibits a high AC impedance with respect to the telephone subscriber line.

Abstract: A control circuit, for use in a telephone switching system, which monitors, controls and transfers data to and from memory, input-output devices and external circuits. A pair of microprocessors and associated read-only and random-access memories are operated in a master-slave arrangement. A comparison circuit continuously monitors the integrity of the master microprocessor by comparing the signal on its data, address and control leads with those of a slave microprocessor.

Abstract: A test fixture including deflectable test probes employing flexible members attaching a probe head to a probe shaft, the probe head engaging a locating aperture to deflect the probe head to a printed wiring board test point not in alignment with the test probe axis. The test probe head may be of conical shape and include a plurality of ribs spaced along an outer surface thereof to reduce friction. The probe head may include a tip which is rounded to reduce test point damage or optionally pointed to achieve fine test point contacting resolution.