[GreenKeys] AN/FGC-38 Torn-Tape Relay Equipment

[Jim Haynes]

The tape-changing reperforator is simply an ordinary one wired into the
same circuit as the regular reperforator - in fact the regular one and
the tape changing one switch roles as the operation goes on.  The tape
changing reperforator is simply turned off until it is about time to
change the tape - then it is switched on, and the other reperf is switched
off at the end of the current message, if any.

If you consider a device like the AN/TGC-1 that has two reperforators and
a three-headed tape reader, one head used for message numbers.  It could
be hooked up to two different circuits (in which case the message
numbering works on only one circuit, as I recall)   Or it can be hooked up
to a single circuit, where the message tape readers work alternately 
(called flip-flop operation sometimes) and the two reperforators can copy
the same traffic, but only one at a time turned on except during the
changeover.  So the whole cabinet can be used for two low-traffic circuits
or one high-traffic circuit.