For synchronization signals of zeroth and first series, a synchronization signal processing system comprises synchronization trunk device of the zeroth and the first series (77(0), 77(1)) for producing particular signals of the zeroth and the first series, respectively, and being exclusively operable in master and slave states. When used in a switching center of a low hierarchy, each trunk device of a local series, which is one of the zeroth and the first series, is supplied as three input signals with the synchronization signals of the local series and a different series with highest (1) and middle (2) degrees of priority and the particular signal of the different series with a lowest (3) degree of priority, selects as a normal signal according to the degrees one of the synchronization signals in the master state and one of the three input signals in the slave state that are normal, and generates as the particular signal of the local series a regenerated synchronization signal with its phase adjusted to the normal signal. A relay trunk device of the local series (95(0), 95(1)) is supplied with the particular signals of the local and the different series with higher (1) and lower (2) degrees of priority and selects as a phase synchronized synchronization signal of the local series according to the higher and the lower degrees one of the particular signals that is normal. In a switching center of a highest hierarchy, the three input signals may be a synchronization signal of the local series produced in a lower hierarchy switching center, the phase synchronized synchronization signal of the different series, and the particular signal of the different series.

System for processing synchronization signals with phase synchronization in a mobile communication network

A time division digital transmission system in which data are transmitted in the form of pulses grouped in multiplex words in time slots forming a recurrent frame. The invention relates more particularly to facilities in transmission line station for sampling from or introducing into the frame data words occupying certain time intervals in the frame. Each station comprises at least a multiplexer, a demultiplexer and a reception time base for restoring from the incoming frames and their framing words the time intervals and addresses of the said incoming frames, so that the component channels can be multiplexed and demultiplexed. Each station further comprises a local time base capable of producing local frames having framing words and the rhythm of which is controlled by the incoming signals, but which is able to oscillate freely in the absence of such signals. A buffer store is alternatively controlled by the received signals and by the local time base, whereby the phase of the outcoming signals is controlled by the latter time base.

Data transmission network with independent frame phase

At a channel bank, such as a D-type channel bank used in the Bell System, a steady visual alarm is exhibited if the source of a detected failure is at a location either within the channel bank or in the digital hierarchy of a digital transmission network. Unfortunately, a craftsperson is unable to distinguish between the two failure locations. To distinguish between the locations, apparatus for indicating the failure location to be in the hierarchy is situated between the hierarchy and the channel bank and, responsive to an alarm failure signal from the hierarchy, extends a predetermined cyclic code signal to the channel bank. Without modification of the channel bank and responsive to the code signal, a cyclic visual alarm in lieu of the prior art steady alarm is provided thereat.

Apparatus for distinguishing between failures in a digital transmission network

In a time-division multiplex digital switching system as for example for PCM telephone exchange utilizing duplicate field installations, the exchange clock pulse generating arrangement is provided in duplicate for the purpose of clock pulse or frequency supply of said coupling field installations, and one arrangement is phase synchronized by the other master frequency determining unit and one exchange clock pulse generating portion supplies one coupling field half in each instance, and the other supplies the other half. The functions of the exchange clock pulse generating portions can be entirely or completely interchanged, as for example, when faults or failures appear in certain portions of the equipment.

Time-division multiplex digital switching network for a PCM telephone exchange system utilizing duplicate connecting field installations

In a data access device for writing into or read from a data conversion table on the basis of a clock signal extracted from a cell being transferred over a line, a clock signal generator of the invention generates a second clock signal which differs from the first clock signal extracted from an incoming cell. A write/read control unit writes data into or reads data for maintenance from the data conversion table on the basis of either the first clock signal or the second clock signal when the line is normal. In the event of the occurrence of a failure in the line, on the other hand, the write/read control circuit permits the data conversion table to be written into or read from for maintenance on the basis of the second clock signal.

Virtual channel converter and VCC table access method

At a main terminal connected to a remote terminal by way of a PCM signal path, a master clock controls the multiplexing of incoming messages from local lines for transmission over an outgoing line of that path to the remote terminal in a bipolar code enabling extraction of the clock frequency at the remote terminal. A discriminator at the main terminal continuously checks the operation of the master clock and, if that operation is normal, causes the transmission of a verification bit over the outgoing line to the remote terminal in an assigned time slot of a service channel of a period message frame; at the remote terminal, a detector responds to either the absence of the verification bit or the nonarrival of message signals to activate a standby clock controlling the sending of composite messages to the main terminal over an incoming line of the signal path. An extractor at the main terminal, connected to that incoming line, delivers the reconstituted pulses of the standby clock to the multiplexer in lieu of the output of the master clock if the latter operates improperly or not at all, as determined by the associated discriminator; a similar discriminator at the remote terminal may insert a corresponding verification bit into a service slot of a message frame transmitted to the main terminal to establish the correct functioning of the standby clock.

M Palombari

Papers

Pcm telecommunication system with standby clock

Schaltungsanordnung zum einfuehren eines ersatz-taktsignals in ein pcm-uebertragungssystem