Using 3 wire tachometer possible without high voltage coil?

Hi.

I'm creating a play dashboard for my son, and have got my hands on an old 3 wire tachometer (Black, Red and Yellow).

From what I can figure out, these are +12V, GND and Signal, and the signal is coming from the Coil of the car it used to sit in.

What voltage would this need to respond, and could I use a simple square wave generator to run it?

gbremset:
Hi.

I'm creating a play dashboard for my son, and have got my hands on an old 3 wire tachometer (Black, Red and Yellow).

From what I can figure out, these are +12V, GND and Signal, and the signal is coming from the Coil of the car it used to sit in.

What voltage would this need to respond, and could I use a simple square wave generator to run it?

If it connected to the coil, it was the primary winding, so it was 12 volts, except when the ignition points opened the circuit to fire a spark plug. If you can get a square wave generator to generate 12 volt peak, then should work.

Paul