Abstract: An interface circuit a.c. couples a transmission line and a port of a telecommunications facility. The transmission line may be of any of n characteristic impedances. The interface circuit includes a resistor network having at least 2n+1 resistor elements. The resistor network is connected to ground by at least one of the resistor elements. A switching device includes at least n switching elements being connected between n of the resistor elements and an input of an amplifier. A transformer includes first, second and third windings, the first winding being for connection to the transmission line, the second winding being connected between an output of the amplifier and a junction between the one of the resistor elements and at least another of the resistor elements, and the third winding being connected between ground and a point in the resistance network other than the junction. A resistor connects at least one of the n switching elements and the port of the telecommunication facility.

Abstract: A hand tool for assisting in the manual closure of integrated circuit (IC) storage and shipping cartridges, includes a base and a shank extending normal from one end of the base and terminating at a grip or stop formation. A pair of tines extends normal from another end of the base, along a direction of the shank. A hinged flap is mounted next to the second end such that it is rotatable to assume a position spaced parallel and extending along the tines. In use, the tines are inserted into an open end of a cartridge full of ICs, with the shank lying along the outer edge of the cartridge and thereafter pressure is manually applied via the tines against an IC to clear a pair of holes in the cartridge and permit insertion of a closure pin through the holes and between the tines. The flap is positioned against the pin to assist in driving the pin into an interference fit. After the pin is inserted the ICs are firmly retained in the cartridge in the well known and desired manner.

Abstract: A typical active impedance line feed circuit includes tip and ring amplifiers being controlled in response to signals at tip and ring voltage taps by control circuit to exhibit a.c. impedance and d.c. resistance characteristics for the purpose of supplying energizing current via tip and ring terminals for tip and ring leads of a two wire communication line. In one example of the active impedance line feed circuit, improved operational tolerance of longitudinal interference and of a ground fault condition is provided by a d.c. amplifier being responsive to voltages at the tip and ring terminals. The circuit is characterized in that an inverting input of the d.c. amplifier is connected via resistors to the tip and ring voltage taps. In operation, the d.c.

Abstract: An amplifier with double rail output being a switchable to single rail output is provided by power pumping circuitry which is controllable by an error detector to deliver modulated power pulses from a d.c. power source to on-following current steering circuits for coupling to either or both of first and second output terminals. In one embodiment the amplifier is envisaged in an integrated circuit form wherein the current steering circuits are provided by switched voltage multipliers of novel structure so that voltage stress of some capacitive elements is reduced, thereby reducing the area these elements would otherwise occupy in the integrated circuit.

Abstract: An amplifier with double rail output being a switchable to single rail output is provided by power pumping circuitry which is controllable by an error detector to deliver modulated power pulses from a d.c. power source to on-following current steering circuits for coupling to either or both of first and second output terminals. In one embodiment the amplifier is envisaged in an integrated circuit form wherein the current steering circuits are provided by switched voltage multipliers of novel structure so that voltage stress of some capacitive elements is reduced, thereby reducing the area these elements would otherwise occupy in the integrated circuit.

Abstract: A CMOS integrated filter includes a passive network of resistive and capacitive paired elements and a first differential amplifier, for implementing a second order low pass filter function. A second amplifier is connected in voltage following configuration at an input of the first amplifier. A filter output is provided by an output of the second amplifier.

Abstract: An AMI signals receiver generates a logic signal stream representative of AMI encoded information signals which have traversed a transmission medium. Adaptive compensation circuits are responsive to characteristics of the received AMI signals for generating a bipolar signal ideally corresponding to the transmitted AMI signal but in practice includes noise primarily caused by near-end crosstalk. An apparent improvement in the signal-to-noise ratio is achieved by generating a unipolar signal from instant and last amplitude samples of the bipolar signal and thereafter differentially decoding a binary signal representation of the unipolar signal.

Abstract: A ferrite core structure for line circuit transformers includes a ferrite spindle for receiving transformer windings, thereby avoiding the need for a separate bobbin as used in conventional line circuit transformers. The ferrite core structure includes a ferrite base for supporting the ferrite spindle and a ferrite cover which fits over the spindle so as to complete a magnetic circuit through the spindle and the base. The base, spindle and cover when assembled define a space for containing the windings.

Abstract: A push and rocker action switch includes a pair of switchable contacts, either of which is switchable in response to a rocker motion of a depressible actuating member, and both of which are switchable at the same time in response to an overall push depression of the actuating member. The actuating member is positioned by an opening defined in a faceplate such that it is centrally supported by a resiliently yieldable pivot. The pivot and the switchable contacts are provided by raised portions in an elastomeric sheet material which is supported by a circuit board fastened to an underside of the faceplate.

Abstract: A handsfree communication terminal apparatus includes a transit switch being controllable for passing signals from a microphone to a transmission interface, during a transmit mode of operation, and a receive switch being controllable for passing signals from the transmission interface to a loudspeaker, during a receive mode of operation. A transmit signal processing circuit followed by a converter circuit generate transmit binary signal assertions in response to syllable-like characteristics in the signals from the microphone. A receive signal processing circuit followed by a converter circuit generate receive binary signal assertions in response to syllable-like characteristics in the signals from the transmission interface. A controller includes transmit and receive bistable circuits, each being clock setable by the respective binary signal assertions and being jam reset in response to the opposite binary signal assertions.

Abstract: A typical active impedance line feed circuit includes tip and ring amplifiers being controlled to exhibit a.c. impedance and d.c. resistance characteristics for the purpose of supplying energizing current for tip and ring leads of a two wire communication line. Protection from excessive heat generation in an instant of a ground fault on the communication line is provided by a d.c. amplifier having an input resistively connected to the tip and ring leads and an output connected via a resistive unidirectional current path to an input of the ring amplifier. A ground fault occurrence causes the resistive unidirectional current path to become conductive and reduces the current flow in the ring lead by causing the output voltage of the ring amplifier to vary in the direction of ground potential. The output of the d.c. amplifier is also useful for improving circuit tolerance of longitudinal interference.

Abstract: An attendant console for use with an electronic private automatic branch exchange (EPABX) includes a jack for removably connecting an attendant headset or handset to the console. A switch array in the console provides indications of attendant control action and logic circuitry connected to the switch array registers the indications. Gates are connected in series with the switch array for preventing registration of the indications in response to the attendant set being disconnected, such that control actions as may be indicated at the switch array while the attendant is away from the console are of no consequence.

Abstract: A supervision filtering function is included in a line circuit wherein tip and ring voltage amplifiers supply energizing current to a two wire communication line via tip and ring primary windings of a transformer and tip and ring feed resistors. The tip and ring amplifiers operate in response to a control circuit which is differentially responsive to resistively coupled voltage signals corresponding to current flows in the tip and ring feed resistors, and which is also differentially responsive to a.c. signals from a secondary winding of the transformer being coupled via a resistive capacitive network to an amplifier in the control circuit. An output of the amplifier provides a supervisory signal. A feed switch is operable by a ring signal to conduct ringing currents to the communication line via the tip and ring feed resistors to the exclusion of the tip and ring primary windings.

Abstract: A variable oscillator, suitable for integration as part of a phase lock loop (PLL) clock source in a complementary metal oxide semiconductor (CMOS) integrated circuit, includes an amplifier and terminals for connection to a tank circuit, for example a crystal resonator. Capacitors are alternately coupled and decoupled in relation to the amplifier to cause oscillatory operation at lower and higher frequencies. In the CMOS circuit the reactance is conveniently provided by conductive layers of predetermined dimensions being carried by an oxide layer. Each layer provides a capacitive reactance which is arranged in series with a field effect device being controlled by associated PLL control circuitry. The control circuit includes a strobe generator for strobing a phase detector in response to a data signal received by an associated receiver. Each time the phase detector is strobed it registers one of an early or late phase indication. The phase indication is used to control the field effect devices.

Abstract: Normal operating range of an active impedance line feed circuit is extended to at least that of a prior art passive resistance line feed circuit. The active impedance line feed circuit includes tip and ring feed resistors in series with outputs of tip and ring amplifiers for coupling a.c. signals to a two wire communication line with an effective source impedance as defined by an a.c. feedback network in response to differential currents in the communication line. Effective output direct current incremental resistances of the tip and ring amplifiers are controlled by a d.c. control circuit connected across the tip amplifier. In an instant of an OFF HOOK communication line of less than a certain resistance a predetermined constant direct current is supplied by controlling the output direct current incremental resistances to be high.

Abstract: A call progress signal monitor includes a translation circuit for generating data signals indicative of predetermined signal characteristics in a TDM PCM signal channel. A processor implemented detection circuit is responsive to the data signals for detecting call progress tones and silence. The translation circuit includes a translation ROM for assigning PCM signal samples with code values in a range with maximum and minimum limits. A comparator generates a comparison value signal in response to the code values of an instant sample and an immediately previous sample. An encoding ROM generates a trend data byte in response to an instant comparison value signal and a plurality of consecutive previous comparison value signals. The instant code value and the instant trend data byte comprise data signals for identification of the progress tones and silence occurrences by the detection circuit.

Abstract: An automatic correction circuit is responsive to suitable bit patterns in a bit stream being received from a transmission medium, to generate an error amplitude map of signal distortion being introduced by the transmission medium. The error amplitude map is digitally stored or recorded. After each non zero bit occurrence in the signal stream a synchronized output signal corresponding to the recorded error amplitude map is generated and added to the bit stream being received to reduce signal distortion, whereby information recovery from the received bit stream is improved.

Abstract: A line circuit includes tip and ring voltage amplifiers each having an output resistively connected via tip and ring feed resistors to tip and ring leads in a telephone line. The tip and ring feed resistors have closely matched ohmic values, and are part of a resistance network which also includes first and second voltage dividers. The first voltage divider is connected in series between the output of the tip voltage amplifier and an end of the ring feed resistor remote from the output of the ring voltage amplifier, and includes a first voltage tap. The second voltage divider is connected in series between the output of the ring voltage amplifier and an end of the tip feed resistor remote from the output of the tip voltage amplifier, and includes a second voltage tap. A control circuit includes a differential input connected across the first and second voltage taps. In operation the control circuit causes the tip and ring voltage amplifiers to provide energizing direct current for the telephone line.

Abstract: A tone source is automatically adaptable in operation to generate tones as required for virtually any TDM telephone system in accordance with stored tone samples being defined to meet the requirements of a particular one of the telephone systems. The tone source provides encoded tone samples from a ROM wherein each tone sequence is stored at corresponding sequential address locations. Each sequence is terminated at unique first and last address locations. The last address location is followed by an address location having an end-of-tone code stored therein. A sample of each of the tones is progressively fetched from the ROM in response to each frame occurrence in an associated operating telephone facility. The first address of each sequence is stored at a corresponding index address location in the ROM. In response to each end-of-tone occurrence the index address of the instant tone sample is read from the ROM and used as a starting point for subsequent fetches.

Abstract: A transformer assisted active impedance line circuit includes a transformer of reduced size as compared to both conventional and d.c. flux reduced transformer line circuits. The transformer has tip and ring primary windings consisting of equal turns and a secondary winding. Tip and ring amplifier circuits each have an output coupled to tip and ring terminals via tip and ring feed resistors which are connected in series with the tip and ring primary windings respectively. A direct current flow, out of the output of one of the amplifier circuits and into the output of the other of the amplifier circuits via two wire communication line connected to the tip and ring terminals, is of an aiding flux-generating effect in the transformer. The secondary winding is terminated by an impedance and provides a.c. signals to which the tip and ring amplifier circuits are responsive to reduce a.c. voice signal current components in the communication line.