TELECOM Digest OnLine - Sorted: Re: TV Show - Legacy Phone in Scene

Re: TV Show - Legacy Phone in Scene
20 Oct 2005 11:47:07 -0700

Joe Morris wrote:

> Question: for postpay systems, what mechanism was used to respond to
> the insertion of coins to turn on the transmitter? Was it merely the
> detection of a coin falling through the mechanism tripping a relay
> (presumably reset when the instrument goes on-hook), or was there
> involvement by the CO (and wouldn't this be necessary if it was
> possible to make long-distance calls from the phone)?

It was a very simple relay set by a change in polarity.

When you dropped in the coins (2 nickels or a dime, the phone held one
nickel until it got a second one) the passing coin(s) pushed on a
lever that turned on the line to the transmitter. The only
involvement of the CO was a polarity switch from the CO that operated
a relay that turned off the transmitter, thus resetting the line.
This meant that both the pay phone and CO gear was much simpler and

All long distance calls (short and long haul) were handled by the
operator. You wouldn't deposit money until the desired party answered.

The more conventional pay phone had a holding area above the coin box
and return slot. That meant CO equipment had to track supervision
(answer or no answer) and keep or return coins accordingly when the
caller hung up. I believe the keep/return signal to the pay phone was
a 100 volt signal and either polarity or ground indicated where the
coins were to go.

As an aside, in the 1970s they had fully _manual_ (no dial) payphones
in Poconos (Penna) resorts. This made sense since most calls from a
resort guest would be long distance and the area didn't have TSP/TSPS,
so an operator would be required to complete the call anyway.

(Mountain Bell used computers to augment toll and assistance cord boards
in the 1970s, a common Bell System practice to stretch old equipment's
usefulness and efficiency. While the operator still worked cords to
connect and disconnect the call, the computer likely handled timing
and ticketing automatically and the operator could likely dial almost
all calls directly using a modern keypad.)

> "Airplane!" was a send-up of the film version of the late Arthur
> Hailey's 1968 book "Airport", which was made into a film by Universal
> two years later. Google shows it as available on both VHS and DVD.

While "Airplane" was intended to be a spoof of the Airport series of
movie dramas, it was based on Hailey's scripts of "Flight into Danger"
of 1956 and "Zero Hour" of 1957 (See IMDB:, as an aside, James Doohan
"Scotty" was in it; see also

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