Short Wave Converter (T987E)

The conversion range of this circuit depends on the coil. The circuit uses two tubes, and the power supply is not provided.

Telegraph manipulator (CB7038E)
This circuit was found in an American magazine 73 for radio amateurs of the 80s. It is an...
Sound activated switch (CB9087E)
Found in American documentation from the 1980s, this circuit can be designed with equivalent...
TTL Logic Probe (CB1461E )
This circuit is from a 1977 documentation. It is powered by the power supply of the circuit under...