This circuit was found in an American documentation from the 1980s. The circuit combines filters of different types in a single structure, each of which can be programmed for a frequency.
We found this circuit in a 1967 Japanese technical magazine. The transistors are made of germanium at...
This two-transistor radio was found in a Japanese publication from the 1960s, with no information on the...
The purpose of this circuit is used in communications and to respond to signals that are in the 2...