This is from a transponder that was available in two voltages and two frequencies. (this is an excerpted portion of the schematic in another thread - "A circuit I don't like")

For the two 9.6kHz versions, the values for T2 are very close to where you could almost use the same part.

But for 12.5kHz, the values for T2 are VERY different. Why would this be? What would be the potential impact of using a 240V part on a 120V circuit?

 

Note that the capacitor, C21, also changes in the 12.5 KHz version but not the 9.6K.

 

I am going to make a guess, which is that there is a great deal more to the reality of the circuit than we see.
By that I am thinking that there are external differences that we are not told about. It is certainly likely that the TS may not be aware of them either.. This would not be the first time this has happened.

 

These boards I have at hand are configured for 240V, 12.5kHz, and my concern was how the circuit would perform if the circuit was rearranged for 120V without having to change the cap and rewind T2 (toroidal transformer).

Or unless it was a different ratio to ensure a stronger signal?