Quote:
Originally Posted by Dave Moll
...so they are respectively "secretary", "line", "transfer (call to other extension)" and "release transfer" - the equivalents on a planset 105/107 being "speak to extension", "speak to exchange", "extension to exchange" and "release".
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Although that would seem the case having one of these phones in my collection and doing some extensive examination of the circuit then wiring a "non standard" extension phone to it the buttons act as follows -
Secy is a latching button which connects the intercom battery/circuit and operates the buzzer in the secretary's instrument, the buzzer in that phone being silenced by an additional gravity switch when the handset is lifted.
Line (or Exch on the 740 version of this phone) does what it says on the tin and connects the Chief phone to, in this case, the PAX line.
I think that the strapping can also be arranged to disconnect the secretary's line access to prevent overhearing if desired.
Trans and Trans rlse are nothing more than a bell transfer switch, when the trans button is operated the bell circuit is disconnected in the chief instrument and "transfers" the bell circuit to an additional bell associated with the secretary's phone - The secretary phone had the option of two lines one exclusive and one shared with the chief.
There is a relay which operates a lamp on both phones to alert an incoming call at any time and particularly when an intercom call is in progress.
The trans rlse button is no more than a latch release for the transfer button
The diagram for the chief instrument can be found
here and the secretary instrument
here
Regards
Andrew