On 16 Mar, 2008, at 17:52, cctalk-request at classiccmp.org wrote: Thank. I presume ECN means PCB = Printed Circuit Board. I should have made it clear that it is the 1301 which is the faster of the two. For example a 48 bit decimal (i.e. 12 digits) add to / subtract from a register takes 21 microseconds. Actually I have two. Serial number 6 was the first one to be sold and was installed in 1962 and it is this one which is assembled and works, though not all the peripherals are functional. Serial number 75 I would guess was made in 1963. I have a few parts of serial number 155, which I would think would be from 1965 when the machines were largely replaced by the ICT 1900 series. Designing of the machines was started in the late 1950s, and many of the engineering drawings have initial revisions from that period. The architecture of your machine reminds me of the first machine I was allowed to operate. It was an 18 bit binary machine, it had 8k of memory built in, expandable with external modules and was made by the Airborne Computing Division (ACD) of Elliotts, it was an Elliott 920B and was a compact, flyable version of the commercial Elliott 903. There had been an earlier model 920A which I think would have been Germanium and was roughly the size and shape of a carpenters work bench. This may have been contemporary with your earlier machine I think. Unfortunately I never saw one in the flesh, but there was a bench in the computer room which I found out later, was the empty chassis of a 920A. Behind the bench was a large panel full of electrical 'chocolate strip' connectors where the analogue and digital input and output signals of the 920A could be connected up. Apparently some of the analogue outputs had been connected up to an oscilloscope to provide a visual display unit, though it used a fair bit of processor time to keep it refreshed, even with the long persistence phosphor of an oscilloscope. The panel had been covered with board with pegs to hold mylar paper tapes and until the day it was scrapped I had not seen what was behind it. What is involved in the restoration? Do you intend to make it work, this would be very hard without the schematics. Roger.