Telephone mute circuit

[kybert]

Hi,

the attached circuit is 'supposed' to work as follows:

The line is connected to the bridge which corrects incorrectly connected lines.

The power supply gyrator filters out all audio ac content leaviong only DC, which is clamped using the zener clamp, then filtered using the caps. This circuit can be used for upto 50uA when on-hook, and 5mA off-hook.

The Handset gyrator allows the handset to connect to the line, allowing the handset to be on and off hook as normal, except it blocks all ac audio content to and from the line, therefore the user cannot hear nor speak to anyone.

Audio can be transmitted to the line by use of the injector in the Line Gyrator.

Audio can be connected to the handset via the dc blocking cap and a limitting resistor.


Can an electronic genus please confirm that my circuit will do what i expect it to do before i build and test it?


Joe

 

[mindctrl]

i know this may sound a little stupid, but... wouldn't it be just as easy to put a small switch in series with the ground wire for the microphone in the handset?

Just thinking.. Anyway, good luck with your circuit!

 

[kybert]

Cant, dont have access to the handset! This is an external device that the handset plugs into ...

It's for a voice reconisition system, the audio is passed from the handset to the processor, where it is checked for keywords (volume up / down etc) then if not detected, it is patched back to the line.

Just need to get the audio and line connections right :shock:

 

[David Bridgen]

I would have thought that C2 needs to be returned to GND for the handset gyrator to have any effect, otherwise any modulation on the line still goes through the handset.
Similarly with the power gyrator, C1 should, I think, also go to ground. And R2 will reduce the gyrator's effectiveness.