Making this into a phone bug?

Thread Starter


Joined Jul 21, 2008
Ok so I built this simple FM transmitter awhile ago.

Here is it's schematic

I am wondering can I replace the electric mic with the input from a telephone green/red wires. I know that the voltage from these wires are around 50 vdc and the current is pretty low. What would I need to get the phone voltage/current in the green and red wires of the phone down to an reasonable level so I can take out the mic and in place put in the input from the phone wires.

Would an audio transformer 1K to 8 ohm work or something because I have that. I want to keep this simple this shouldn't take alot of circuitary to replace the mic with the input of the phone.
Thanks for any help.
I don't want to create a totally new FM transmitter just want the ability to use the input voice signal of a phone instead of the mic in my transmitter to modulate with.

So don't give me knew schematics for totally different FM transmitters or stuff.

Also I know I would have to take account of the 90vac 20hz ring so as to not damage the transmitter when this occurs.

Thanks for any help


Joined Apr 25, 2008
The roof,the washer and phone you may tilt the computer to,all In
fun.If you can't take a joke. (Blast Me)

Thread Starter


Joined Jul 21, 2008
Funny :)

Ya, I like this stuff , what did tesla say a man has 2 reasons for doing anything the right reason and his real reason.

But seriously , what would you have to do to convert the telephone line voltage/current into the equivalent mic level input in the transmitter circuit? I don't think I can directly hook the green and red wires into where the mic was. (think this high voltage would destroy the circuit )

What would I have to convert could I use an audio transformer or something?