Ideas for a Trimphone switch

[JWatler]

Hello

Unable to find a blanking plate for the front of a dial 722 Trimphone, I have slotted in a Switch No. 13A-2 (“Single pole, non-locking, change over”). Although this serves the purpose from a cosmetic point of view, I wonder if it would be possible to connect the switch to do something useful such as temporarily silencing the microphone during a call. My extremely limited knowledge of electronics is such that I don't have a clue what is or is not feasible. I would be very grateful for any ideas and/or guidance.

I attach some images of the present set up.

John

[julie_m]

Try connecting the blue and slate grey wires from the switch, to the blue and white wires from the handset (T3 + T10 with standard wiring). This will give a muting function while the switch is held down.

[JohnBHanson]

Best to use the switch as a change over with a 300 ohm resistor to keep the microphone circuit ok.


eg

300 ohms
+-----white---microphone----blue-------+--------\/\/\/\/\/\/\----------+
| | | +---------------------------------------------/\----------------------------+
switch



Hope that helps....

[julie_m]

I doubt that's strictly necessary. The dial off-normal contacts just short-circuit the microphone.

[bobbyball]

I have used a switch to silence the microphone in several Trimphones - due to the design of the handset, covering the holes at the bottom doesn't work! Just connected across the blue and white wires works fine...

Robert

[JWatler]

Thank you all for the comments. I have now connected the blue and grey wires from the switch to T3 & T10 and it works perfectly.
Many thanks
John