US 4,229,816 AGranted

Timing signal generation and distribution system for TDM telecommunications systems

AssigneeRedcom Laboratories, Inc.

InventorsCharles J. Breidenstein, Jerome S. Caplan, Bruce G. Littlefield

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Abstract

Synchronous operation of any number of digital switching units of a TDM system is maintained by interconnecting the switching units to a timing signal highway which distributes timing signals generated by sources of such signals in any one of the units. The units are connected successively in a chain by timing signal distribution control lines. Validity signals are generated and transmitted by circuits in each unit along the lines so as to provide for transmission of timing signals generated in the first switching unit on to the timing signal highway and switch over of the timing signal generating function to successive ones of the units when the timing signal generation in preceding units becomes faulty.

Claims20

Dependent claims

For use in a time division switching system having a plurality of synchronously operable switching units connected to highways carrying messages, control signals and timing signals, a system for generating and distributing said timing signals which comprises

a plurality of lines interconnecting said units successively in a chain,
separate sources of said timing signals in each of said units,
separate fault detection means in each of said units responsive to the operation of the source therein for applying a signal representing whether or not the source therein is faulty to the one of said plurality of lines to its next succeeding one of said units,
timing signal validity detecting means in each of said units, connected to the one of said lines to its immediately preceding one of said units and responsive to the signal thereon for applying said signal to said one of said lines to its next succeeding one of said units, said signal also representing whether or not the sources in all of its preceding units are faulty,
means in each of said units, operated by said validity detecting means therein when said signal on said one of said lines to its immediately preceding one of said units is representative of said sources in all of its preceding units being faulty, and also operated by said fault detection means therein when said source therein is not faulty for enabling the transmission of said timing signals from said source therein onto said timing signal highway.

2 more elements

In a system having a plurality of units operable in synchronism with each other, a system for the generation and distribution of timing signals which comprises a timing signal bus connected to each of said units for distributing said timing signals thereto, a plurality of timing signal validity signal lines, separate validity signal generation and transmission circuits in each of said units, said circuits having inputs and outputs, said signal validity lines being connected between said inputs and outputs such that said units are connected in succession via said validity lines, each of said units having means for generating said timing signals, said validity signal generation and transmission circuits comprising means responsive to the presence of a validity signal at said input and the valid operation of said timing signal generating means for providing a validity signal at said output when at least one of said validity signals at said input and valid operation of said generating means is present, and means for applying the timing signals from said generating means to said bus when said validity signal at said input is absent.

Dependencies are inferred from the claim text.