Abstract: A digital signalling receiver translates pulse code modulated (PCM) tone signalling into a signal format compatible with a controller in an associated time division multiplex (TDM) telephone switching facility. In the receiver, steering signals are generated in synchronism with the operation of the switching facility to direct the operation of a time shared filter. The filter performs a plurality of filter functions with a series of PCM signals received from the TDM switching facility and generates therefrom series of filter signals relative each of the filter functions.

Abstract: A digital telephone signal interface circuit couples data signal from one digital telephone facility, operating at one data bit rate, to another digital telephone facility operating at another data bit rate. The interface circuit includes a storage system and a frequency converter circuit. The frequency converter circuit includes an analogue frequency converter circuit for multiplying the frequency of a signal applied thereto by a whole number and a digital frequency converter circuit for reducing the frequency of a signal applied thereto by a factor of at least two. The analogue and digital converter circuits are connected in series and generate a second synchronizing signal for the operation of the other digital telephone facility in response to a first synchronizing signal from the one digital telephone facility.

Abstract: The invention provides a circuit for converting M-bits of an input data word having M+A bits in addition to an input parity bit, to B-bits of an output data word having B+A bits in addition to an output parity bit. A code-conversion circuit is responsive to the input M-bits for generating a converted data word having B-bits plus a secondary parity bit which gives the converted data word a parity value the same as that of the input M-bits. The secondary parity bit is exclusive-ORRED with the input parity bit to produce an output parity bit which renders the parity value of the output data word the same as that of the input data word.

Abstract: A tone receiver, for receiving audio frequency tone signals typically used in telephone signalling, includes a reference frequency generator and a modulator for up-converting audio frequencies. Telephone network tone signalling is up-converted and coupled to a filter including a piezoelectric element. Alternating current signals passing through the filter indicate the presence of a tone signal of a predetermined frequency. Multiple frequency tone signals are detectable using a plurality of modulators and filters, each modulator being supplied with one of a plurality of reference frequencies. In one example, balanced modulation is used with reference frequencies being supplied in the form of square waves.

Abstract: A clinching machine for clinching the leads of a connector on a circuit board includes a top wall which provides a work surface having an opening for receiving the leads and a clamp for clamping the circuit board and the connector in place against the work surface. A pair of clinching jaws, each having a pair of work faces intersecting at an angle of less than 90.degree., are pivotably mounted in fixed relationship adjacent to the opening. Pneumatic actuators first cause the clamp to engage the circuit board and the connector, and then cause the jaws to pivot, thereby drawing the leads into close contact with land areas on the circuit board. The amount of rotation of the jaws corresponds to the difference between the intersecting angle and 90.degree..

Abstract: Trunk and line circuits packaged as modules are provided with circuitry for generating self-identifying type-code information which is retrievable on request by the central control unit of the system. The received information is compared with the type-code information contained in the data memory of the central control unit. Upon non-correlation between the received and the stored type-code information, an alarm signal is generated. In the described embodiment, the type-code information generating circuitry on each board comprises a voltage level source individual of the type of board and an analog to digital converter circuit associated with the board.

Abstract: A clock signal generator is responsive to a signal having a pulse repetition rate, and to a word instruction to generate a new signal having a pulse repetition rate according to the word instruction. The clock signal generator in one embodiment is capable of providing a plurality of clock signals each according to an associated word instruction.

Abstract: A two-stage switching network is provided wherein the two stages are interconnected by a pseudo space switch. The input and output ports of the network, each comprising a plurality of channels, are partitioned into groups each one of which is common to a time division switch. Each switch comprises a serial-to-parallel or a parallel-to-serial converter circuit, a data memory and a connection memory. The space switch comprises a commutator circuit for sequentially and periodically connecting each of the input switches to each of the output switches once for each channel. The commutator comprises a plurality of layers corresponding in number to the number of bits in each PCM word.

Abstract: A circuit for shifting a binary data word having N-bits any number up to N-1 positions left or right is described. A shifting network having a plurality of levels for shifting a binary word a predetermined number of positions in only one predetermined direction is cross-connected to a register such that the register stores the mirror image of the binary word appearing at the output of the shifting network. The output of the register is connected back to the input of the shifting network. By passing an input data word twice through the device, it can be shifted left or right any number of positions.

Abstract: The invention provides a telephone line circuit in which the likelihood of exposing circuit devices in an associated switching facility to potentially damaging currents or voltages is greatly reduced. A repeat coil includes a primary winding for connection to a subscriber loop circuit. Direct loop current is maintained in the primary winding and the resulting d-c flux is compensated for by a regulator including a balancing winding. The core material in the repeat coil is saturable and limited in bulk to that sufficient to transmit normal a-c voice signals across the line circuit. Signals of a magnitude which cause the core material to saturate are thereby impeded in transmission across the line circuit.

Abstract: A digital circuit for the level measurement of PCM signals representing an analogue signal and encoded in accordance with a predetermined companding law comprising a selector circuit having position 0-n for selecting integers between 0 - n; a sampling circuit for successively sampling the input PCM signal 2.sup.n times, n being determined by the selector circuit; a connector circuit for converting each of the samples to its normalized power representation and for computing the average power of the samples; and means for determining the signal level equivalent of said average power in a conventional representation of power levels.

Abstract: A universal receiver/sender is achieved by providing circuitry having parameters setable by binary data words from the data processing unit of a switching facility. A clock signal generator provides output signals corresponding to respective binary instruction words whereas the parameters of an analogue signals receiving circuit are controlled by binary control words. A plurality of commutating filter circuits receive pass band limited analogue signals from the receiving circuit and under control of signals from the clock generator provide binary output signals indicative that a signal within a predetermined pass band has been received. Also provided is a data store for storing the required instruction and control words as well as the output signals from the filter circuits.

Abstract: A TDM PCM communication system includes a plurality of user terminals, a switching network and a CPU for controlling the establishment of transmission paths between the user terminals and the switching network for the transfer of information between predetermined ones of the user terminals. An incoming path carries information bits from the user terminals to the switching network and an outgoing path carries information bits from the switching network to the user terminals. The switching network includes means for transferring single information bits each residing in a time slot period from the incoming path to the outgoing path. The transferring means includes an exchange means for effecting a bilateral exchange of information bits in fixed pairs of time slot periods, whereby paths for information bit transmission are periodically provided between ones of the user terminals, as determined by the CPU.

Abstract: A switching circuit includes a magnetically latching relay and associated contacts connected between a subscriber loop and associated subscriber equipment. In one state of latched operation the subscriber equipment is connected to the loop via the contacts and in the other state of latched operation the subscriber equipment is disconnected from the loop. To operate the relay a voltage is applied to the loop, the voltage being of sufficient value to charge a capacitor in the switching circuit to the threshold voltage of a PNPN diode which is connected in series with the operate coil in the latching relay. The PNPN diode discharges the capacitor through the operate coil to cause the relay to latch magnetically in a make or break state depending upon the polarity of the discharge current. An AC resonantly responsive relay is added to the switching circuit to selectively inhibit switching circuit response in the case where more than one switching circuit is utilized on a loop.

Abstract: A telecommunications terminal apparatus, connected to a transmission facility which includes a source of energizing current and an earth connection, is protected from static discharge of the type typically originating with a user. The terminal apparatus includes an ABS housing with one or more apertures therein to facilitate user actuation of various control buttons or keys. The periphery of each aperture is rendered electrically conductive. A low impedance sink such as a remote power supply, earth or a transmission line is connected to the electrically conductive periphery via a variable impedance element, for example a pair of back to back zener diodes. The housing also includes a conductive foot for contact with a supporting surface. The conductive foot is also connected with the conductive periphery of the aperture.

Abstract: A multiple frequency signalling receiver translates combinations of tone signals received from a telephone set to derive binary two out of eight coded signalling. Received signals are directed by a filter to high and low band translator circuits. Each translator circuit includes a circuit for deriving a threshold signal from the received signal and a threshold signal controlled limiter for limiting the received signal. The threshold signals are cross coupled between the limiter in each translator to prevent response to signals in the high and low bands being substantially unbalanced in amplitude. Digital counting and decoding circuits in each translator circuit detect predetermined frequencies of signals from the limiting circuits. Upon occurrence of a consistent detection by both the translator circuits lasting for at least about 40 milliseconds, the appropriate two out of eight code is gated to the output terminals of the multifrequency receiver.

Abstract: An interface circuit adapted to selectively input serial and parallel PCM coded words and to selectively output serial and parallel PCM coded words is connected to a memory means. The memory means has a storage capacity for at least 2.sup.n memory words, each one having an address corresponding to a respective one of the PCM coded words appearing at the interface circuit and each one representing X db of signal level variation relative to its corresponding coded word. The output of the memory means is connected back to the parallel input of the interface circuit. A control means provides timing and control signals for loading the interface circuit with one of the coded words and for causing the memory means to be addressed at the location defined by the coded word. The control means includes means for circulating the coded word through the memory means a predetermined number of times M.

Abstract: A circuit for suppressing noise pulses generated by the transfer of a charged telephone line from one supervisory circuit to another is provided. A capacitor is first connected to the telephone line and is charged to the voltage level appearing across the telephone line at the one supervisory circuit. The telephone line is then transferred from the one supervisory circuit to the other supervisory circuit and the capacitor is disconnected from across the line.

Abstract: Fraudulent toll telephone calls are detected by the recognition of extraneous supervisory signals which are generated in the originating office in response to a perpetrator placing such a call. The invention provides a means of detecting a second proceed-to-send signal received at the originating office and of recording in memory means the identities of the calling and called parties. Timing means for achieving the detection is connected to the automatic message accounting trunk circuit of the originating office and, upon detection, an MF receiver is also connected thereto for a predetermined interval of time.

Abstract: Power is fed from a pair of power supplies to each one of a plurality of load circuits through a distributed power switch. A plurality of switch means are each associated with a respective one of the load circuits for connecting it to one of the power supplies in a primary manner and to the other power supply in a secondary manner. Upon failure of its primary source of power, each switch means is effective for automatically connecting its load circuit to its secondary source of power.