Abstract: A fault monitoring and diagnostic system for a telephony switching system. Two call processing systems connect through a programmable switch to port group units that receive individual telephone lines. All signals from the port group units are conveyed to both call processing systems, and the call processing systems operate in synchronism. However, the programmable switch conveys signals back to the port group units from only one of the call processing systems. Fault monitoring and diagnostic circuitry monitors various conditions within the telephony switching system. A test call generator automatically performs test calls thereby to diagnose system problems. If a fault is detected, the fault monitoring and diagnostic system controls the programmable switch and, in appropriate circumstances, couples the output signals from the other call processing system to the port group units. Information concerning the nature of the fault is also provided.

Abstract: In a digital data transmission system including one or more matrix switches in which data in digital form is stored in a send memory during one selected time slot of a recurring time frame, transferred to a receive memory and sent out from the receive memory during another time slot of the recurring time frame to establish desired data paths through the switch between selected inputs and outputs, means is provided in the form of a programmable read only memory to control the insertion loss of each data path in a selective manner.

Abstract: An operator complex in which control signals relating to key lamp and alphanumeric display operation and key transition data are carried between the operator console and the PABX system on a multiplex highway or radio transmission link to permit virtually unlimited spacing between the operator console and the associated switching system. The operator console includes a send control system and a receive control system. The send control system detects valid key transitions and formulates a message concerning such detected key transmissions to be sent to the common control in the PABX. The receive control system receives messages from the common control indicating key lamp or alphanumeric display information and decodes these messages to effect selective control over the display.

Abstract: A digital conference circuit provides greater stability in voice transmission by selectively inverting the signal in alternate conference channels, thereby providing cancellation of parasitic echo signals which tend to create oscillations or ringing. Selective gain control is also provided for conferences of different sizes and efficient use of conference lines is ensured by providing for selective combination of conference groups.

Abstract: An electronic equivalent of an X-Y switch is provided using time division multiplex techniques. The basic switch includes a multiplexing section and a control section, the control section responding to signalling information received on the multiplex line including dialing impulses to determine each successive digit as it is dialed for controlling the steering of voice and signaling information through the multiplexing section to an output of the switch designated by the received digit on one of a plurality of free levels determined by a selected time slot. Thus, a switch having plural outputs with plural levels on each output electronically operates in the manner of the known X-Y switch but with reduced physical size and lower maintenance requirements.

Abstract: An air-fuel ratio control system for an internal combustion engine utilizes an oxygen sensor to maintain a 14.5/1 air-fuel ratio at a first location in an intake manifold to an engine combustion chamber. A method and apparatus is disclosed for adding fuel and/or air to the air-fuel mixture at a second location, between the first location and the engine combustion chamber, so that the engine operates at a high economy, low emission point when idling, running at a substantially constant speed or decelerating and operates at a low economy point, yet still with low emissions, only when accelerating.

Abstract: A unitized shelf and guide framework for supporting so-called printed circuit cards in spaced alignment. Open-work shelves are joined, for example by welding, in accurate alignment to corner posts to form a frame. Each shelf consists of longitudinal channel members extending in parallel array between end flanges, and may be formed by punch press of a single piece of metal. The channel members are covered by split sheathes, which may be molded of a plastic, and which carry transversely extending alignment bosses for guiding and positioning the circuit cards. A wired back plane of the usual kind is secured in predetermined alignment behind each shelf, and carries the usual receptors for the pin terminals that extend from the back edges of the cards.

Abstract: A levered inject-eject cam device is provided for pivotal mounting at the upper and lower corners of the rear edge of a printed wiring board. The cam is constructed of an integral molded body member having a bifurcated configuration which forms branching members which receive the wiring board therebetween. The branching members form flat stock members and the cam is formed as a profile shape of these flat stock members to engage a fixed engageable strip which extends toward the edges of the printed wiring board from the frame of the wiring board cell. A tyne is integrally molded into each branching member to resiliently grasp the board. The tynes provide sliding friction which permit the cams to be prepositioned before the wiring board is inserted into the cell so that the cams will be in proper position to cam the engageable strip, and not be in an undesired position in which the cam lobe strikes against the engageable strip and prevents insertion.

Abstract: Centralized toll restriction for private branch exchanges (PBXs) is performed by providing first and second memory addresses in the number translator of a central office switching system. The first and second addresses are matched with restricted telephone calls and unrestricted telephone calls, respectively. Those telephone lines of each PBX which are to be restricted are marked in a convenient manner, such as with tip to ground marking, while those telephone lines not restricted are left unmarked. Outgoing trunks between the PBXs and the central office switching system are temporarily marked with an unbalance upon going off-hook on a restricted telephone line, in order to transmit restriction indication to the central office switching system.

Abstract: A system and methods are disclosed in which two telephone calls are terminated simultaneously provided that one call is a local call and the second call is a trunk call and further provided that the local call and trunk call originate in separate line units. This is made possible by dividing a central office telephone switching system into two halves wherein each half includes both number translator circuits and code translator circuits and wherein each half includes both local register groups and trunk register groups. An allotter alternates between the register groups in each half of the circuit while indexing the register groups in order to match a local call placed in one-half of the circuit with a trunk call placed in the other half of the circuit for simultaneous termination.

Abstract: A digital circuit for converting a delta modulated signal to a binary coded signal without producing an interim analog signal. The principal portions of the circuit are an up-down counter, a read-only memory the instantaneous output of which is controlled by the up-down counter, logic for driving the up-down counter in response to an incoming delta modulated signal, and a scanner for producing time-spaced pulses in response to the instantaneous outputs of the memory. A comparator is also included for driving the up-down counter relatively slowly to compensate for drift by ensuring that, over relatively long periods such as a few seconds, the output of the up-down counter oscillates around its mid-value.

Abstract: An air-fuel ratio control system for an internal combustion engine includes an air intake connected to a burning chamber having an oxygen sensor and an intake manifold to an engine combustion chamber. Fuel is mixed with air in both the air intake and the intake manifold. The oxygen sensor maintains a 14.5/1 air-fuel ratio in the mixture in the air intake, and a pressure differential sensor equalizes the pressures in the air intake and the intake manifold. The rate of flow of fuel into the intake manifold is varied so that the engine operates at a high economy, low emission point when idling, running at a substantially constant speed or decelerating and operates at a low economy point, yet still with low emissions, only when accelerating.

Abstract: A circuit for eliminating possibly false signals such as those due to contact bounce in electromechanical devices from a stream of digital pulses that represent the instantaneous states of selected conditions at successive intervals. The circuit includes a majority logic detector, two stores, one for storing the input signals, and one for storing the output of the majority logic detector, and means for feeding the input signals and the outputs of the two stores to respective inputs of the detector for comparison.

Abstract: A circuit is provided to convert a set of mutually exclusive digital signals representing presence or absence of individual tones of a Dual Tone Multiple Frequency (DTMF), or 2-of-8 signal, system into a four digit binary code word. Each different four bit word combination represents a different valid tone combination of the DTMF signal system. The four bit binary code word is represented by digits stored in an output register which serves as an output buffer. The loading of the output register is controlled by a single, multiple function signal which: (i) incorporates a coincidence timing function, (ii) provides a validity check which is also an integral part of the logical operation of the conversion, and (iii) causes the output signal to be interrupted upon a shift in input tones even though the shift in input tones may occur without interruption.

Abstract: Analog detection of invalid signal conditions at the input to a Dual Tone Multiple Frequency (DTMF) tone receiver is provided. The average of the voltage peak amplitudes of the signals in the upper and lower bands of the DTMF signal are crossed compared, and if the level in one channel exceeds that in the other channel, or if the level in one channel exceeds that in the other channel by a ratio greater than approximately 3:1, the tone receiver output is inhibited. Also, such an average of the voltage peak amplitudes in the portion of the frequency spectrum above 1700 Hz. of the tone receiver input is compared with the same averages of the high and low bands, respectively. If either of these latter comparisons indicate the ratio of the input component above 1,700 Hz. relative to the respective band signal is greater than approximately 0.25, the tone receiver is inhibited from providing an output.

Abstract: A tone receiver for detecting a Dual Tone Multi-Frequency (DTMF) signal includes first and second digital tone detectors for the high and low bands, respectively. These detectors are of the type which employ the period detection technique. Each detector has a set of outputs corresponding to the valid tones in the respective band. A latching flip-flop is associated with each output of each detector. A coincidence timer is provided to insure that there are outputs from each of the detectors for a predetermined duration of time. The coincidence timer is reset by any change of any of the latching flip-flops from a state representing absence of the tone to a state representing presence of such tone. The latching intervals are determined by zero-crossings, which define the periods involved in the period detection operation.

Abstract: A digital tone detector is of the period detection type employing a digital counter which is stepped by means of a high speed clock. The counter is reset by zero-crossings of an analog tone signal. A set of period range decoder gates indicate the presence of any of a set of predetermined frequency tones. A .div. 4 counter is introduced between the terminal which receives the zero-crossing signal and the reset input of the counter. Sequence control circuits are provided to coordinate the timed relationship of readout and initiation of a new detection period such that the speed of response is minimally degraded by the .div. 4 counter.

Abstract: A respective bus monitor circuit is connected to each group of a plurality of circuits selectively connectable to one end of a multi-conductor bus which extends to a common control circuit. When the function to be performed by the common control circuit is not completed within a preset time, all bus monitor circuits are signalled to check the group of circuits to which they are individually connected to locate a possible malfunction therein and automatically disable that group to prevent lock-up of the system if the malfunction is detected.

Abstract: A difference amplifier, the construction of which includes operational amplifier, has an extended amplitude range of common mode signal. The input of the circuit which is applied to the inversion input of the operating amplifier is applied to the latter through an attenuation network. An adjustment of the other resistor values in the circuit is made to appropriately retain the desirable characteristics of keeping common mode rejection.

Abstract: A printed circuit card adapter for mounting on an elongated stud comprises a bar-like member having at least one surface area having a contour substantially conforming to the surface of the elongated stud upon which it is mounted. Guide means are disposed on the member for receiving an edge of a printed circuit board. The longitudinal axis of the guide means is disposed substantially parallel to the longitudinal axis of the member. An embodiment of the adapter employs a web to join together pairs of members to produce a strip comprising a plurality of adapters. Means are provided in the web for enabling one to readily divide the strip into one or more adapters as required.