Patent GB-1276156-A (GB)
Title: An arrangement for a telecommunication exchange
IPC: H04Q11/04
Filed: 1969-07-02
Abstract: 1276156 Automatic exchange systems PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 2 July 1969 [5 July 1968] 33353/69 Heading H4K. A non-blocking TDM switching network includes in respect of each incoming highway a cyclic store in which the data from each channel of a frame is compressed into a single time slot and is then repeatedly recirculated for a time equal to the number of channels on an outgoing highway. In order to connect an incoming channel to an outgoing channel, control logic closes a crosspoint switch during a time slot related to the outgoing channel so that all the recirculating data is passed (without cancellation of the recirculation however) to a buffer where the data in respect of the wanted incoming channel only is temporarily stored prior to its transmission to the outgoing channel. Each highway carries thirty two, 8-serial bit PCM channels having a frame time of 125 Ásec (8 KHz) and a time slot length of 3À9 Ásec. After synchronization in an incoming circuit the eight bits of each channel of one highway are applied in parallel over the leads 117 to a parallel/serial converter 300. (Parallel connections from the incoming circuits of other highways are represented by leads 118). During the time slot t<SP>1</SP> following their reception in the converter, the eight bits are read-out in turn by pulser e 1  ... ej on 32 successive occasions by 37 sub-time slot pulses Aw 1 -Aw n . A comparator 306 is supplied with the channel number A t  to which the eight bits relate and also successively with the sub time slots Aw. When coincidence occurs the bits are gated into recirculating store 32. Data from the other channels of the one highway is gated into the store 32 in a similar manner during the next 31 time slots so that eventually the store contains data from all the channels which data is recirculated once per time slot. After 32 time slots from entry viz a frame, further recirculation of the first channels eight bits is inhibited by closure of gate 303, gate 301 being simultaneously opened to allow entry of the data occurring during the channel's second frame and so on. A central processor (not shown) determines which incoming channel shall be connected to which outgoing channel. The addresses Aal and Aul of the respective highways carrying these channels are inserted in registers 500 and 501 (Fig. 5). The incoming channel identity Aak is incremented by 1 (to allow for the delay in inserting its data into store 302) and the resultant A<SP>1</SP>ak is inserted in store 500 while the outgoing channel identity Auk is decremented by 3 (the reason for which will appear) and the resultant A<SP>1</SP>uk is inserted in store 501. An address register produces the numbers of the outgoing channels in turn over lands At. When coincidence with A<SP>1</SP>uk occurs, a control signal corresponding to Aul is passed by one of gates 505 ... 506 to a control circuit 115 ... 116 allotted to the particular outgoing highway Aul. Whilst this control signal exists, the incoming highway identity and the modified incoming channel member Aal, A<SP>1</SP>ak are inserted into a recirculating store 509 of the indicated control circuit e.g. 115. (Each store 509 can contain up to 32 such identities and it recirculates them once per frame.) Once the identities are stored in 509, the registers 500, 501 can be cleared for subsequent use by the central processor. The considered word Aal + A<SP>1</SP>ak advances through the store and once per frame it is passed by a series/parallel converter to a register 512 where it is stored at a time slot A<SP>1</SP>uk+1. Consequently the crosspoint e.g. 404 corresponding to the connection Aal to Aul is opened by a signal over lead 513 and the total contents of circulating store 302 (viz the eight bits in respect of each of the 32 channels of the one highway Aal) are supplied to a word selector 110. It will be remembered that the eight bits corresponding to a particular channel are stored during a sub time slot having the same member as the incoming channel number. Consequently by comprising the identity A<SP>1</SP>ak with the sub time slots AW in comparator 515 a control signal will be derived for causing selector 110 to extract only the relevant eight bits from the mass of data presented thereto via the crosspoint. The extracted bits are passed over leads 119 to an outgoing channel circuit at time slot A<SP>1</SP>uk+2 preparatory to their transmission along the correct outgoing channel at A<SP>1</SP>uk+3 viz Auk. When the call finishes, the data pertinent thereto in recirculating store 509 is cancelled by writing zero into register 500 and the word Aul+A<SP>1</SP>uk into register 501. In the manner described above, the latter word will cause zero to be written in place of Aal + A<SP>1</SP>ak in store 509. The single matrix 109 may be replaced by a multistage non-blocking space division network when many incoming and outgoing highways are to be interconnected.