This circuit is from American documentation from the 1980s. The circuit can make use of any common NPN transistor and the power comes from two small batteries.
This traditional detector configuration is from an old publication where the MC1555 is the...
This two-transistor emitter-coupled oscillator circuit with capacitive feedback was found in the...
If the reader is skilled, he can mount this spy micro-transmitter with SMD components and obtain an...