This interesting circuit uses a sodion valve that we have already described in an article on the website. The circuit uses several batteries for power. The phone is of high impedance.
We found this 4W transmitter in a Mullard transistor manual from 1960. The circuit is powered by...
This circuit was found in a 1977 Radio Handbook. The MOSFET supports an equivalent. Capacitor C must...
This simple alarm was found in a 1982 documentation, but uses components that are still common,...