Abstract: Apparatus, and an accompanying method, for transmitting a frame synchronization signal and a data signal simultaneously through a serial transmission medium (170). Specifically within a data transmitter (105), a frame synchronization signal, a clock signal and a data signal, are encoded to form a single bi-phase mark signal having the frame synchronization signal incorporated into the bi-phase mark signal as a phase-shift. The bi-phase mark signal is then transmitted through a suitable serial transmission medium. A receiver (175), connected to the transmission medium, receives and amplifies an incoming bi-phase mark signal appearing on the medium, and, in turn, synthesizes the clock, frame synchronization, and data signals from this bi-phase mark signal.

Abstract: Apparatus, and an accompanying method, for transmitting a frame synchronization signal and a data signal simultaneously through a serial transmission medium (170). Specifically within a data transmitter (105), a frame synchronization signal, a clock signal and a data signal, are encoded to form a single bi-phase mark signal having the frame synchronization signal incorporated into the bi-phase mark signal as a phase-shift. The bi-phase mark signal is then transmitted through a suitable serial transmission medium. A receiver (175), connected to the transmission medium, receives and amplifies an incoming bi-phase mark signal appearing on the medium, and, in turn, synthesizes the clock, frame synchronization, and data signals from this bi-phase mark signal.

Abstract: Apparatus, and an accompanying method, for transmitting a frame synchronization signal and a data signal simultaneously through a serial transmission medium (170). Specifically within a data transmitter (105), a frame synchronization signal, a clock signal and a data signal, are encoded to form a single bi-phase mark signal that is defined by a specific modulation protocol and the frame synchronization signal is incorporated into the bi-phase mark signal as a protocal violation. The bi-phase mark signal is then transmitted through a suitable serial transmission medium. A receiver (175), connected to the transmission medium, receives and amplifies an incoming bi-phase mark signal appearing on the medium, and, in turn, synthesizes the clock, frame synchronization, and data signals from this bi-phase mark signal.

Abstract: A line switch including a concentrator arrangement for coupling telephone calls between a plurality of subscriber lines and a plurality of port group highways to a central office switching network in a telephony system. The analog voice signals are first digitized and multiplexed into time slot channels on line group highways for transfer to the concentrator arrangement. The concentrator arrangement couples the digitized voice information signals between time slot channels on any of the line group highways and any of the port group highways. The line switch includes control circuitry that selects the time slot channel, line group highway and port group highway to couple the digitized voice information signals between the subscriber line and the central office matrix switch through the concentrator.

Abstract: A telephony network with a digital central office and one or more remotely located digital satellite units. Each digital satellite unit connects to a number of remote subscriber lines and monitors these lines to establish communications through interconnecting spans and a digital satellite interface at the digital central office. The digital satellite interface includes a programmed controller that communicates with the remote digital satellite units connected to it, with call processing equipment in the digital central office and with maintenance processing equipment in the digital central office. Supervisory information and voice data information, in digital form, pass through span equipment that interconnects port group highways in the digital central office and the interconnecting spans. The span equipment strips messages from and inserts messages into signalling time slots on the interconnecting span.

Abstract: A telephony network with a digital central office and a one or more remotely located digital satellite units. Each digital satellite unit connects to a number of remote subscriber lines and monitors these lines to establish communications through interconnecting spans and a digital satellite interface at the digital central office. The digital satellite interface includes a programmed controller that communicates with the remote digital satellite units connected to it, with call processing equipment in the digital central office and with maintenance processing equipment in the digital central office. Communications with the maintenance processor are in the form of messages having a header byte and a byte indicating the length of the message. During network initialization and various recovery operations, the programs and/or the data base can be transferred from the maintenance processor to each digital satellite interface through the use of these messages.

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 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: Digit analysis within an electronic private automatic branch exchange telephone system is carried out through interconnected sections of digit decoder circuitry. A first portion of the digit decoder effectively processes dialed impulses originating within the PBX system and determines whether or not the call is to be directed to another line within the system, to a trunk or to the attendant. The contents of an ING and ED memory are continuously monitored and modified, where necessary on a time shared basis with the other calls processed by the system. Direct inward dialing and listed directory number analysis is carried out in a second portion of the decoder which also causes the ING and ED memory to be monitored and modified, where necessary for the processing of the digits. For either internally directed or externally directed calls, the sequentially received digits are initially processed in the units position of the memory and appropriate action is taken as the result thereof.

Abstract: A timer circuit receives a multi-bit digital signal representative of a timing code to be incremented. In dependence upon the coded value of the received signal, the code represented by the signal will be incremented at a selected clock rate. The clock rate selected may be chosen to decrease in frequency in a stepwise manner as the code is incremented. As the timing interval increases, the percent resolution of the timing code is maintained substantially constant.

Abstract: A trunk adapter is associated with a common control private automatic branch exchange telephone system for interfacing the system with a central office. Four different types of adapters are associated with the system to effect a ring-down incoming, loop start outgoing trunk connection, a ground start type trunk connection, a two-way dial-to-dial trunk connection, and a two-way E and M signalling interface. To provide a buffer between the ring and tip circuits the adapters employ optical coupler circuits. The adapters are controlled by the common control on a time shared basis and operate independently of the state of the sleeve lead.

Abstract: A circuit for detecting a true seizure condition of a trunk calling bridge relay employs a timer which is incremented every 40 milliseconds as long as a continuous trunk off-hook representative signal is supplied thereto for approximately 300 milliseconds. For momentary changes in the condition of the trunk CB relay the timer will be incremented and decremented so as to effectively filter out momentary trunk calling bridge seizure changes.

Abstract: An electronic private automatic branch exchange may avoid the need for access trunks and information trunks in the operator complex by utilizing a single stage switching matrix to effect connections between line circuits, trunk circuits, and the operator under control of the common control. To accomplish this the operator line circuits are provided and operator loop circuits as line appearances at the inputs of the matrix. In addition, the common control is provided with recognition circuitry for recognizing a request from a line for connection to the operator or a request by the operator for connection to a line and conversion circuitry for converting such requests to a multidigit designation of the operator line circuit or loop circuit to be acted upon by the system in the manner of a connection of a line circuit.

Abstract: In an electronic private automatic branch exchange telephone system, busy test is carried out by way of a two step process. Initially, a junctor memory is scanned and the called number is compared with each ING and ED number contained in memory. At the completion of the scan and comparison a check of the calling bridge relay of the called number is made. Associated with the busy test arrangement are camp-on and call-waiting features which may also be carried out during the test.

Abstract: A local transfer arrangement for an electronic private automatic branch exchange having a space divided rectangular solidstate switching matrix is disclosed. The local transfer arrangement is provided with means for sensing a local transfer indication from either a calling station or a called station connected by a local junctor. The transfer indication causes the system to forward the transferring station to a second local junctor and hold the first local junctor. A transferee station is then signaled via the second local junctor of the impending local transfer by the transferring station. Thereafter, an automatic forwarding of the transferee station to the first local junctor is initiated by an on-hook condition of the transferring station to complete the operation. Additional features of the arrangement provide for a return to the original call and release of the connected junctors responsive to an on-hook or hookflash condition of the transferring station.

Abstract: A tie trunk control arrangement is disclosed for providing tie trunk connections in an electronic private automatic branch exchange which is built around a space divided solid state matrix. Each tie trunk has an associated tie trunk junctor dedicated thereto which may be connected to local stations by the PABX system in a manner similar to other trunk junctors. For incoming tie trunk connections an attendant extension or station attendant extension is used for providing connections to other PABX stations and trunk circuits. Common circuitry used for trunk transfer and trunk consultation may be used by the station attendant to extend the tie trunks to the PABX stations and the outgoing trunk junctors. Further circuitry is provided by the tie trunk control arrangement to allow a tie trunk and a central office trunk to be tandemed in the system or to allow two tie trunks to remain tandemed in the system without attendant supervision.

Abstract: An electronic private automatic branch exchange is built around a space divided solid state matrix. One side of the solid matrix provides line appearances which are connected to line circuits, tone receivers, senders and operator loops. The other coordinate side of the matrix provides junctor appearances for connection to an attendant junctor, local junctors and trunk junctors. The solid state switching matrix is a single stage matrix providing direct connection between line appearances and junctor appearances by the closing of a single crosspoint, and connection between lines within the system is effected simply by the interconnection of a pair of crosspoints associated with the respective lines and a selected junctor, thereby providing a greatly decreased switching for establishing a connection through the matrix. The control necessary for effecting such connections is provided with much simpler common control equipment than is utilized in a conventional multistage switching network.