Abstract: Bipolar violation error counters are rendered insensitive to bipolar violations arising from the presence of bipolar eight-zero suppression (B8ZS) patterns in a bipolar pulse train by detecting B8ZS patterns in the pulse train applied to the error counter, and zeroing those bits of the B8ZS pattern which produce bipolar violations.

Abstract: Malfunctions in an automatic span line switch due to resonances in high-speed span lines are avoided by interposing signal-free intervals whenever the switch causes a possible phase change to occur in the signal being supplied to the span, preventing the transmission of partial signal pulses, and using quasi-random code and keep-alive signals. Unnecessary phase changes are avoided by verifying the validity of data before allowing it to be put on the span following a data loss; disabling the error detection circuitry for a limited time following a switching operation; and preventing the switching of low-priority span on standby if the failure has been remedied during the standby period.

Abstract: A method and device for phase synchronization for use particularly where a fixed internal clock signal generator is used for both receive and transmit functions.The phase difference between the incoming pulse train and a fixed internal framing clock is detected by a counting circuit which provides an output signal indicating the interval time of the phase difference. A delaying means coupled to the incoming pulse train delays the same in response to the output signal for the time indicated thereby and provide synchronism therebetween.

Abstract: A telephone subscriber testing system is disclosed in which all tests may be performed from a central office. A central office test device is connected to the central office by a separate telephone line with a telephone number of its own. Moreover, a dedicated command channel connects the office test device with a remote test device over the carrier lines. This dedicated channel is used to communicate commands and transmit test results back to the central office. By causing the remote device to "dial up" the office device, the entire trunk loop through the PCM trunk and the central office switching equipment can be tested directly in one measurement at the central office.

Abstract: In an all-digital telephone system for communication between a central office and widely scattered subscriber locations, means are disclosed for carrying digital service from the central office to various distribution locations over T1-type equipment and from the distribution locations to subscriber locations over ordinary two-wire lines using time-shared bidirectional pulse code modulation.A salient feature of the system is the provision of "smart repeater" means which permit unidirectional or bidirectional access between any digital subscriber line and any channel of the T1 line under the control of the central office. Provisions are also made in the system for the transmission of slow-speed signals suitable for the remote reading information from sensing devices at the subscriber locations and for the remote operation of suitable devices at the subscriber locations.

Abstract: The standard D3 signalling frame bit pattern of a T1-type PCM telephone system is modified to provide a pattern in which (4n-3) separate low-speed data channels can be transmitted in a superframe consisting of 12n frames of the PCN carrier (n being a positive integer), without requiring a separate synchronization detector for superframe synchronization. Simple self-synchronizing circuit means are further disclosed for multiplexing a large number of essentially steady-state signals onto the low-speed data channels, and for positively detecting the onset and cessation of each steady-state signal, independently of the onset and cessation of any other steady-state signal, once in each group of k superframes, where k-1 is the number of steady-state signals being multiplexed.

Abstract: A switching system is disclosed for the concentration of a plurality of telephone lines onto a lesser plurality of intermediate trunks, wherein an independent processor is included at both ends of the concentrator system. These processors communicate with each other over a randomly chosen idle trunk, thereby negating the need for a dedicated communication link between the processors. Each processor controls the switching functions at its end of the concentrator, independently monitors and retains trunk status, subscriber line status and system operational status, and provides system fault detection, diagnosis and recovery including communication to maintenance personnel of trouble codes based on the detected fault and its diagnosis. Manual interaction with the system is also enabled at either end of the concentrator system via display and input/output units or remote from both ends.

Abstract: An essentially non-dissipative, strap-free, continuously adjustable power unit inherently impervious to shorts and open circuits for powering repeaters in a T1 or similar telephone span line is disclosed. The unit uses a pulse-width modulated inverter in the converter input circuit to produce a variable-voltage D.C. output to the span line. The pulse width or duty cycle of the inverter is controlled by a control logic which senses the span line current and maintains it at a selectable predetermined level without any apreciable power dissipation.

Abstract: Conventional PCM encoders are made capable of handling a much larger number of telephone channels than normally possible by varying the set-up interval of the encoder in accordance with the maximum signal level to be set up.

Abstract: An automatic span line switch for PCM communication lines is disclosed which isolates alarm conditions to an actual span line failure, as distinguished from failures in the terminal equipment. In addition, the switch uses a specific code transmission to provide fast switching and to permit identification of the direction of failure. Although the circuit is capable of switching span segments individually and independently, it can transmit an alarm to a distant central office and automatically establish an appropriate test loop in the presence of test transmissions when needed to permit single-end troubleshooting. The switch further tests the dead line continuously and stringently for error-free data transmission, and automatically resets without disturbing traffic when the trouble has been corrected. An extremely flexible priority system for selected channels is also provided, and the circuitry on both ends of all channels (including the protective channel) is identical to minimize parts inventory costs.

Abstract: A data processing system for monitoring a telephone switching system comprises a microprocessor controller, random access and read only memories, and data input and error output means. The data processing system analyzes the received data to determine if the switching system is operating correctly, and if it is not outputs coded information indicating the errors discovered and methods for switching system repair.