Hi Nigel,
When you said "transformer" I first thought you're kidding me
Then I search the net for US with transformer and found one circuit at
www.ednmag.com
I made the circuit in the attached file, search for an audio transformer in my over-aged stuff and found a small transformer, not greater than 1.5cm³
Primary winding = 44.5R (with middle tap 23.6 and 24.2R)
Secundary winding = 3.7R
Is this valid data for an audio transformer
?
First part of 556 makes 40kHz signal
Second part makes signal 100ms high / 1ms low
Gates from 4093 combine both signals to 1ms with 40kHz burst every 100ms.
Gates from 4049 makes, or better, are supposed, to drive the transformer so that I have .... Vac for the transmitter.
Since I measure Ohmic values on boh sides I suppose it's a good (audio) transformer.
Can you please tell me what I am supposed to measure at the secundary side of the transformer because I measure nothing with a scoop.