CIRCUIT ARRANGEMENT FOR COMPENSATING THE PHASE DIFFERENCES BETWEEN THE DISTANCE CLOCK ON A PCM TIME MULTIPLEX LINE CONNECTING TO A PCM SWITCHING CENTER AND THE OFFICIAL STOCK OF THIS SWITCHING CENTER

摘要

A pulse coded time division multiplex (PCM) telecommunication system has two non-synchronous clock pulse trains for controlling information transfer and switching operations, respectively. In a circuit arrangement for compensating phase differences resulting from deviations between both clock pulse trains there is arranged an intermediate store for externally controlled buffering of PCM words for half of a pulse frame and connected thereto a buffer store for internally controlled buffering of PCM words for a full pulse frame. The intermediate store is designed for two modes of operation under control of the external clock pulse train. In an active mode during one cycle at first a stored PCM word is read out and is then replaced by a new PCM word. In the second mode the same PCM word first is temporarily buffered and immediately read out thereafter. Change of operation is controlled by a control unit monitoring addresses for alternate read operations and write operations of the buffer store of a minimum off-set of selected addresses to obtain by skipping of half of a pulse frame sufficient off-set without continuous uncontrolled slippage losses.