Patent GB-1293514-A (GB)
Title: Time division multiplex telecommunication switching system
IPC: H04Q11/04
Filed: 1971-04-19
Abstract: 1293514 Time-division-multiplex switching systems PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 19 April 1971 [25 March 1970] 24849/71 Heading H4K Each outgoing highway of a time-division- . multiplex pcm switching system is served by at least three pcm code stores read out sequentially and cyclically to constitute the outgoing bit stream, pcm codes being directed to the stores by selective switching between the stores and an associated super-multiplexed intra-system highway. Incoming highways 100, 101, 102, in groups of eight are multiplexed on to a respective primary intermediate highway 113, 115, 116. The 32-channel 8-bit incoming highways of each group of 8 highways feed one 480-channel, 8-bits in parallel, intermediate highway. In each incoming highway frame the pcm codes of the highway group are switched over 108 to a buffer store 112 of 480 compartments holding a pcm code and an associated channel and highway address code in each compartment. The channel and highway addresses originate from synchronizing units 107 and reach store 112 over separate highway 109-1, highway 109-0 routing the pcm codes. The synchronizing units 107 introduce a variable delay in order to effect alignment of channels across the highway group 100 and the units also convert the serial pcm codes to parallel pcm codes. A cyclic register 114 addresses and reads out the compartments of 112 to form the pcm code stream in the 480-channel capacity of intermediate highway 113. A space-division switch - 117 controlled by channel address stores such as 121 and decoders 122, 123, 124, connects any channel of a primary intermediate highway to a free channel in any one of the secondary intermediate highways 118, 119, 120, depending on which group of outgoing highways 128, 129, 130 is-required. Each secondary intermediate highway gives access to a respective group of outgoing highways, such as 128-0 to 128-7, served by a transmission distributer, such as 125. Each highway of the group is served by its own group of pcm code buffer circuits such as 134. Address register 132 selectively gates channels of the secondary intermediate highway 118 to particular outgoing highways according to requirements, and address register 480 steers such channels to an appropriate one of the four pcm code buffer stores 135-0 to 135-3 serving each outgoing highway. The buffer stores are read out consecutively under control of register clock 140 to constitute the outgoing serial pcm code stream on a 32-channel per frame basis. As each frame contains 480 intermediate highway channels and, in any time slot, only three of the four pcm code buffer stores are available for receiving a code as one of them will be in process of being read out, each outgoing channel is accessible to only 45 intermediate highway channels and each intermediate highway channel has access to only three outgoing channels of each outgoing highway. The periods of accessibility of the buffer stores, and their periods of read-out with respect to a full 32-channel outgoing highway cycle, are explained with reference to Fig. 2 (not shown). An exchange clock is described with reference to Fig. 3 (not shown).