This circuit with unijunction transistors was found in a documentation from the 80's. The trigger times of the SCRs depend on the capacitors and are adjusted in the 5M (4M7) potentiometers.
It can be obtained from Mouser Electronics the new MAX14871 Maxim consisting of a full-wave...
This circuit provides 2.5 W of power with 6 V supply and 4-ohm speaker. We found it in the Radio...
The integrated circuit used in this detector is uncommon today. We found it in a documentation from the...