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I have a latching switch and I want to know if there is anyway I can change the switch, so that when it is pressed the circuit is open, but when it is released the circuit is closed.

The situation is I have a PTT button which shorts out the mic+ and the GND which mutes the mic, but for this to work I have to have the button pressed in.

Can I make it so it is muted without the button pressed, without using a normally closed momentary switch?

enter image description here

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  • \$\begingroup\$ What are you using it on? If it's POC, they all have different PTT protocols which are momentary, so the mic isn't shorted during the talking. \$\endgroup\$ Commented Apr 23, 2020 at 19:46
  • \$\begingroup\$ Jordan - The title and part of question say the switch is latching. Then you say that the switch in question is a PTT (push to talk) switch, and every one of those I have used, is a momentary switch. Therefore the existing switch which you have to interface with, is unclear. I can think of 3 improvements you could make, by editing the question: (a) Include any possible solutions (in addition to using a momentary NC switch as you mentioned), which you have considered and eliminated - and why; (b) Add a wiring diagram (even a photo of a hand-drawn one) showing connection & switch details. \$\endgroup\$ Commented Apr 23, 2020 at 19:51
  • \$\begingroup\$ Its card to explain due to the nature of it but in a nutshell its a basic inline latching switch acting as a PTT button for a aux cable which plugged into a phone. The circuity is complete with using 100uf capacitor and 100k resistors and it all works. The circuit also works fine with a NC momentary button but the latching switch which i am talking about for the circuit to work it has to be pushed in so i am wondering if there is a way to reverse that \$\endgroup\$ Commented Apr 23, 2020 at 19:53
  • \$\begingroup\$ [continued] (c) Please clarify what you mean by "de-pressed". You seem to use it as the opposite of "pressed", but often "pressed" and "depressed" are synonyms. Do you mean "released" instead of "de-pressed"? Please edit the question to make this clear. Thanks. \$\endgroup\$ Commented Apr 23, 2020 at 19:54
  • \$\begingroup\$ Sam- I am aware that a NC momentary button can be used and this has all ready been done but unfortunately for the application in which this is intend to be used it has to be a latching switch \$\endgroup\$ Commented Apr 23, 2020 at 19:55

2 Answers 2

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You may use an SPDT / 1P2T slide switch.

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You could think out-of-the-box and switch the microphone ON with that switch. Then add a resistor to keep the line more or less quiet when it is not connected. Something like this:

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ I have added the circuit that i have in the question. \$\endgroup\$ Commented Apr 23, 2020 at 20:25
  • \$\begingroup\$ Oldfart - The problem i had with that is my phone didn't recognize that there was a mic connected when it was cut off then when you pressed the button it popped and you could speak. Do you know any way round this? \$\endgroup\$ Commented Apr 23, 2020 at 20:27
  • \$\begingroup\$ The resistor might fool the computer in thinking there is a microphone, but you may have to play with the value. Also I don't know exactly if this will work with an electret microphone. But it costs only a few cents in resistors to try. \$\endgroup\$ Commented Apr 23, 2020 at 20:30

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