I went for a dig in the stack
IS731 IS248 and IS749 are the same manual they all have the same section
574-123-100TC issue 1 May 1969 33 Call Control Unit, General
Description and Operation
probably worth scanning
PC12 is the parts catalogue section 574-123-800TC 33 call control unit
(UCC) issue 6 December 1970
good exploded views and part numbers
IS732 has an earlier version of the call control doc that also covers
the 32 as well as 33
574-123-101TC Issue 2 October 1964 32 and 33 Call Control Unit
Principles of operation
some circuits of sections to explain operation
First glances are no full circuit or inter unit wiring info unfortunately
Dave Caroline