I don't know how the phone company recorded charges back then.
> According to the Eng & Sci history, AMA tapes included message unit
> calls, so detailed records were available even if not shown on the
> customer's bill. But message units could also be easily recorded on
> the same meters used to track local calls, just incrementing the
> counter as needed per call. AMA was developed with No 5 crossbar in
> 1948 so it was theorectically available for NY.
The counters (one for each phone line) simply clicked off as needed. I have no idea how they got the feedback to "know" whether to just click once for a local, untimed, call -- or whether to click twice on start, once every three minutes (or some other arrangement ...) depending on distance.
NY Tel had a camera that literally was pushed against a (dozen at a time?) counters and the numbers were then processed by someone or another and added to the bill.
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