With this circuit you can produce the sound effect passing from one channel to another. The circuit is from Mullard documentation from the 1960s. The transistors may be the BC548.
This metal detector circuit uses an AM radio as an indicator. The radio is placed off-station and tuned...
This high quality circuit with complementary symmetry was found in an Electronics World of 1966....
This circuit was found in a 1980s telecommunications publication. The circuit uses a diode bridge to...