Directly below the CPU is the Power Supply, and beneath that, our PB-250 is configued with Multiverter, Digital To Analog, High Speed Buffer, and Ampex Core Memory units.
The CPU keeps a running total of hours in use.
The CPU is constructed using a number of very simple logic boards, with a custom wired backplane to impliment the PB-250's logic. The backplane is soldered, rather than wirewrapped, and each socket is keyed to only allow the insertion of the correct type of board.
It has a very minimal front-panel built in:
It primarily relies on the console Flexowriter for many of the operations one would expect to be on the front panel for a machine from its time.
The PB-250 was part of a hybrid digital/analogue computer called the Trice system offered around 1960 by Packard Bell Electronics.
We currently know of only three PB-250s still in existance:
Ours (The Retrocomputing Society of Rhode Island)
The Computer History Center's
An excellent recollection and description of the PB-250, from someone who used one in a production environment.