Found in a 1924 publication, this 2-valve receiver has a speaker output. Power comes from several batteries. Information about the coils is given.
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,...