ICL 1900 Series Computers

Photograph courtesy Atlas Computer Laboratory, Chilton

The photograph shows part of a mainframe communications setup, with a what appears to be a line termination frame (with patching facilities) on the far left, a telephone switchboard in the center, and 2 frames of model shelves with 6 modems per frame on the right. There would have been more modem frames and another frame containing the line termination units for the communications processor, with switches and status lights for each channel. The line termination frame and modems would be supplied by the Telco (GPO Telephones - telephones were part of the Post Office, a Government monopoly, as in most European countries, before being privatised as British Telecom).

A variety of remote peripherals were available, ranging from a simple teletypewriter, through single VDUs, VDU Clusters to Remote Job Entry stations; connected via telegraph lines or telephone lines and modems at speeds from 10cps to 4800cps, using asynchronous and synchrous protocols (depending on type). Local VDU controllers were directly connected to the 1900 series processor via a standard peripheral interface.