Ethan Dicks wrote:
If it's an ITT or other non-Western Electric
phone, I'd wager it's
IC-based. AFAIK, only the W-E phones (i.e., pre-breakup) would have
the 1-transistor-2-coil keypad.
As indicated in my previous message on the topic, Automatic Electric was
producing a 1-transistor DTMF design in the 60/70's, almost identical to WE's.
--
I don't know what it was like in the Bell/WE regions, but out here DTMF, while
available, didn't really take off until sometime in the late 70's/80's I
would
say, perhaps in correlation with the switch to IC-based DTMF. I'm guessing the
number of 1-transistor DTMF phones produced was relatively small,
(particularly) compared to the number of dial phones produced in the same time period.