This circuit uses a crystal phone and can be built with more modern transistors like the BC548. The original circuit is from a 1979 publication and is powered with only two AA or AAA batteries.
Based on common components, this circuit was found in an English publication. The circuit is...
This circuit is from Mullard 1969 documentation. The circuit operates at a relatively high supply...
In relation to the previous circuit (CB18493E) this spy has an extra transistor, which can be a...