This circuit, which can be seen elsewhere on this website, was obtained from a 90’s English documentation. The circuit drives a small speaker, but for greater volume an external amplifier must be used.
This amplifier was found in a Japanese publication in 1972. Transistors are uncommon today, and...
The current of this source is 200 mA at the most, and the output depends on the zener that may...
Found in Mallory documentation from 1968 this circuit uses an integrated circuit from that time. The...