This circuit was found I a 1965 Radio Schack documentation. The transistors are from that time, admitting equivalents. The transformer has 500 ohm primary and secondary depending on the speaker.
This circuit was found in a Mullard transistor manual from 1960. Note the symmetrical power...
This amplifier step with a transistor has an input impedance of 100k to 10 M. The transistor can be any...
I found this little signaling transmitter in old American documentation. The circuit has a good...