INTERNATIONAL TELEGRAPHS This web site is to remember Post Office and BT services and people who provided these services from the 1950's to the 1980's

MRC Revision Computer

After a difficult start the MRC settled down to relaying large numbers of telegrams automatically but there was still a problem of lost messages and this resulted in the investment in a Honeywell DDP516 computer which was called the ‘Revision Computer’. It’s job was to monitor the hundred plus input and output lines to and from the exchange and check that every message which entered the system exited correctly.

The 516 was a 16 bit mini-computer with 64KB of ferrite core memory and a 750ns Cycle time. In an age where most computers didn’t have more than a couple of serial line connections this 516 was fitted with two HCMLC’s (High Capacity Multi-Line Controllers) which could monitor up to 256 telegraph lines at the same time.

There was no way to get the 516 up the stairs to it’s new home on the first floor so it had to be craned in through the window.

Plenty of people ready to welcome the new computer

Almost ready for the first tests. Here you can see the 516 control panel used to enter information into the registers and run the programs and on the right the High speed paper tape reader capable of reading at up to 1000 characters a second.

Thanks go to Ted Copper for all the pictures on this page.

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