Patent GB-1446655-A (GB)
Title: Communication switching system
IPC: G06F15/16
Filed: 1974-03-11
Abstract: 1446655 Data transmission systems INTERNATIONAL BUSINESS MACHINES CORP 11 March 1974 [21 March 1973] 10710/74 Heading H4P A modular communication switching system with distributed control includes an interface incorporating line registers 11, 11a-11z, Fig. 1, to each of which a communication line X1-XN can be connected and arranged to assemble a data block, processor modules 19, storage modules 21, and a loop network of interconnecting branches L1, L2, L4-L6 on which data blocks can be transferred from each line register 11 to each processing module 19, from each processing module 19 back to each line register 11, from each processor module to each storage module and from each storage module to each processor module. An extracting means 13 gates from its line register 11 into the network any data block and each processor module 19 not containing a data block is capable of accepting any one passing data block from the network for execution and for transmission under the control of the control data contained in that data block and for subsequent re-entry into the network. Each line register 11 has a capacity of one frame and a scanner 13 extracts a frame from a line register 11 and passes a data block via an entrance interconnection branch L1 to a decision unit 17. The decision unit responds to a direct transfer indicator bit contained in that data block to feed that data block via a direct path L3, an exit interconnecting path L2 and a distributer 15 into a line register 11 identified by an address contained in that data block. If direct transfer is not indicated then the decision unit 17  passes the data block to the processing path L4 for entry into the first free processor module 19 for processing and transmission under control of the control data contained in that data block via path L6 to the exit interconnection L2. A feedback branch L9 is provided so that a frame which did not find a free processor 19 is fed back to L5 again so as to enter the first free processor 19. Further interconnecting branches L7, L8 are provided so that data blocks can be transferred from each processor module 19 to each storage module 21 and from each storage module 21 back to each processor module 19. The storage modules 21 temporarily store data for which the capacity of a frame is not sufficient and permanently store common converting tables. The storage modules 21 allow special services such as automatic repetition of dialled numbers, dialling with abbreviated numbers, accounting, reversible dual connections and multiple connections. A more detailed system of Fig. 1 is disclosed (Figs. 2a-2c, not shown) which includes line register modules (31-31n) each including 100 line registers and each line register module (31) having one scanner 13 and one distributer 15. Each processor module 19 has a program storage module (53) in which instructions for all processing steps to be performed by the processor module are stored. A further path (L11) is provided for frames which have to be handled again by the processor. A repeat branch (L12) is provided for returning a frame that could not be accepted by a storage module 21. Busy indicator modules (75) are provided for storing the availability status of a communication line. A busy indicator byte corresponding to the called line is inserted into the frame and interpreted later on by a processor module. A peripheral processor (93) is included together with peripheral devices (91) such as consoles, magnetic tape or disc storage units and outprinters. A time of day clock (83) in digital form is provided which is useful for accounting and further clocking units (T1-T5) are provided.