Where is the Mic in This Circuit ?!

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The speaker works in 2 modes. It works as a microphone when the push-to-talk switch is pressed (at your end), and as a speaker at the far end.

No extra microphone required.

It is interesting that power comes from the far end, through the speaker. Quite a clever circuit.

EDIT: oops.... ericgibbs got there first
 
Last edited:
hexreader said:
The speaker works in 2 modes. It works as a microphone when the push-to-talk switch is pressed (at your end), and as a speaker at the far end.

No extra microphone required.

EDIT: oops.... ericgibbs got there first
Click to expand...

hi R,
You've got be quicker than that.!
 
OOOPS .... thanks for your swift answers.

Is this a special type of speaker/Mic ? or a separate speaker and a Mic to be connected in parallel ?!

Thank you
 
aljamri said:
OOOPS .... thanks for your swift answers.

Is this a special type of speaker/Mic ? or a separate speaker and a Mic to be connected in parallel ?!

Thank you
Click to expand...

hi,
Its only a speaker, most speakers will work as a 'crude' microphone.

Note the impedance of the speaker
 
Last edited:
aljamri said:
Ohh my God, Is that true. Can I use my 8 Ohms speaker as a mic ???
Click to expand...

That circuit specifies a 25R to 125R speaker..

But your 8R would work on a suitable amplifier, try connecting the speaker leads to a scope and talk into it..
 
ericgibbs said:
That circuit specifies a 25R to 125R speaker..

But your 8R would work on a suitable amplifier, try connecting the speaker leads to a scope and talk into it..
Click to expand...

Even large PA speakers work quite well as mikes - amazing what you can use for an emergency bass drum mike
 
A speaker used as a mic makes a very boomy sound due to its resonance.
Gas stations have a very cheap intercom at the pumps that use a 45 ohm speaker.

Google and most of the world never heard of a 25R speaker. They know about a 25 ohm speaker instead.
 
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