Abstract: A secretarial answering system for use with a switching system which includes a plurality of subscriber telephone stations each equipped with a buzzer, and a secretarial telephone station equipped with an audible signalling circuit and a plurality of lamp and switch pairs. A line circuit is connected to each subscriber station and monitors its busy, idle and ringing status. A processing unit periodically scans the line circuits to determine changes in the status of the subscriber stations. This processing unit then transmits subscriber station status and identification information to the secretarial telephone station. The secretarial station uses this information to provide visual and audible indications of subscriber station status. In response to operation of the switch associated with a called subscriber station, a directed call pick up or a call transfer message is transmitted by the secretarial station to the switching system.

Abstract: A secretarial telephone station for use with a secretarial answering system and a switching system which includes a plurality of subscriber telephone stations each equipped with a buzzer. The secretarial answering system is connected to the subscriber stations and transmits subscriber station busy, idle and ringing status and line identification information to the secretarial station. The secretarial station includes a lamp and switch pair for each subscriber station, a processing unit and an audible signalling circuit. The processing unit receives this information and causes the lamp associated with each of the subscriber stations to display dark, lit or flashing signals corresponding to the idle, busy and ringing status. The processing unit also causes the audible signalling circuit to provide a ringing tone wherever a lamp is flashed.

Abstract: A switching isolated single transistor forward converter which performs demagnetization and snubbing functions with the same network. The transformer stored energy and the energy stored during snubbing are transferred to the load by the network during the dead time of the switching cycle.

Abstract: A protective circuit consisting of two diodes which functions along with other external circuit elements to provide protection against transients for an integrated circuit utilized to generate dial pulses in an electronic telephone circuit. By means of included diodes, excessive transients are prevented from entering the integrated circuit internal circuitry and disturbing the memory included therein or other operational characteristics.

Abstract: A transformerless telephone circuit including an integrated circuit pulse dialer and transmit, receive and ringer circuitry employing discrete components. Included in the transmit, receive and dialer circuitry are fixed resistive components, which in combination with each other present a constant impedance to said telephone line.

Abstract: A circuit which controls access of host and remote processors to a single memory. A first flip-flop indicates acceptance or refusal of the processor's memory access requests. A second flip-flop provides a wait signal to the host processor when the remote processor is accessing the memory. A gating circuit causes the first flip-flop to accept the remote processor's access request when both the host and remote processors request memory access at the same time.

Abstract: An arrangement for connecting a terminal pin to a printed wiring board conductor via an electrically conductive elastomeric collar positioned about the terminal pin and pressed into a plated through hole connected to the conductor. Ridges are formed on an outer surface of the collar and a tapered lead-in is provided at one end of the collar to permit engagement with and the formation of contact areas between the collar and the plated through hole. The collar additionally may include a drive shoulder at an end opposite the end containing the tapered lead-in. Projections may be formed on the terminal pin which engage cavities formed in the inner wall of the central bore within the collar to retain the terminal pin within a collar. The collar may be of electrically conductive or electrically non-conductive material.

Abstract: A speech synthesized time announcement circuit for use with a telephone line control circuit. Upon detection of a predetermined number of ringing signal bursts or a predetermined keypad provided data pattern or a predetermined time period, a control microprocessor determines the current time of day and forms a time-of-day message by retrieving selected digitized words from a read-only memory. This message is transferred to a speech processor which converts it to analog format. If the time of day request was received over a telephone line, the control microprocessor causes the speech processor to answer the line and couple the time-of-day message onto the line. If the request was received by internal interrupt or via the keypad, the control processor causes the speech microprocessor to announce the message locally by applying it to a local speaker.

Abstract: A printed wiring board file employing guide tracks of wire construction to engage guide runners of printed wiring board assemblies to be mounted therein. The guide tracks are assembled to lateral positioning members at regular or optionally, predetermined differing spacings and each guide includes a forwardly projecting divergent lead-in area to assist in aligning the board assembly guide runner with the file guide tracks. A pair of depressions are formed in each guide track to engage corresponding projections in the guide runners to retain the board assemblies in their fully inserted position within the file.

Abstract: A circuit which eliminates race conditions caused by gate delay variation. In the absence of gate delay variations data is made available for a period of time which extends beyond commencement of processing of such data. This circuit prevents gate delay variations from causing processing to commence after the period of time during which data is available. Each of a pair of flip-flops initiates or terminates the data available time period. These flip-flops, an exclusive-or gate and related circuitry are arranged such that the period of time for data availability is not terminated until after processing of such data actually commences.

Abstract: A memory access selection circuit including a microprocessor, address, data and control multiplexers, a random access memory, storage circuits and related logic circuitry. This circuit allows both an external processor and the microprocessor to receive data from and transmit data to, the random access memory. The microprocessor controls access of the external processor to the random access memory by controlling and monitoring the multiplexer and storage circuits. This prevents erroneous data, address and control signals from appearing at the memory when switching between the microprocessor and the external processor as sources to the memory.

Abstract: A double file printed wiring board module arranged to mount printed wiring boards on both sides of a centrally positioned interconnect or side plane while providing for the convection cooling of the printed wiring boards and the interconnection of same with conductors of minimal length. The printed wiring boards are supported by a connector at one side edge and a board guide at an opposite side edge. The interconnect or side plane includes an external termination connector mounted at its rear edge to permit the efficient connection of the circuit module to external terminations.

Abstract: A printed wiring board file employing printed wiring board guides positionable within the file at a plurality of first predetermined spacings and further positionable at a plurality of second predetermined spacings in increments different from those of said first showings. A tab at one end and a clip at the other end of each printed wiring board guide permit assembly to support members and further permit the removal of same should it become necessary to reposition printed wiring boards within the file.

Abstract: A clock selection circuit which selects and enables one of a plurality of clock circuits in response to initialization by a processing unit or detection of failure of an on-line clock circuit. The clock circuits are selected on the basis of a priority arrangement. The clock circuit failure is detected by a retriggerable monostable multivibrator and the selection priority is based on time delays generated by programmed counters associated with each clock circuit.

Abstract: A circuit which unlocks the signaling circuit of a feature telephone station after it has been locked. A microprocessor disconnects a tone generator from an associated keypad upon detection of operation of a lock button. The microprocessor subsequently connects the tone generator to the keypad upon detection of operation of the lock button and a predetermined master unlock code provided via the keypad. The microprocessor also connects the tone generator to the keypad upon detection of operation of the lock button followed by simultaneous operation of a predetermined plurality of telephone feature buttons.

Abstract: A printed wiring board assembly including a printed wiring board including a pair of guide runners attached to an upper and a lower edge thereof. The guide runners include an elongated body, a pair of elongated walls extending the length of and from one side of the body, and a groove formed the length of and on a second opposite side of the body. Projections extend from one of the elongated walls through apertures in the printed wiring board to retain the guide runners in engagement with the board. Protrusions extend into the groove and engage depressions in guide tracks of an associated printed wiring board file to lock the board assembly in its fully inserted position within the file.