Where is the Mic in This Circuit ?!

[aljamri]

The circuit below has no Mic, anybody knows where to connect ?

**broken link removed**


The circuiut is at the end of this page:

http://www.talkingelectronics.com/te_interactive_index.html

 

[ericgibbs]

hi,
The speaker is used as a mike. dual function.

 

[hexreader]

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

 

[ericgibbs]

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

hi R,
You've got be quicker than that.!

 

[aljamri]

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

 

[ericgibbs]

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

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

Note the impedance of the speaker

 

[aljamri]

Ohh my God, Is that true. Can I use my 8 Ohms speaker as a mic ???

**broken link removed**

 

[ericgibbs]

Ohh my God, Is that true. Can I use my 8 Ohms speaker as a mic ???

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..

 

[Nigel Goodwin]

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..

Even large PA speakers work quite well as mikes - amazing what you can use for an emergency bass drum mike

 

[aljamri]

I do not think that I came across such speaker, I've googled for "25R speaker" and got

"25R speaker" -

 

[audioguru]

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.