The transistor on this mixer can be any general-purpose transistor. The number of entries can be changed. We found it in an old documentation. Input and output cables must be shielded.
According to the author of this project, from a documentation on espionage from the 1980s, this...
This circuit suggested by Siemens can provide time intervals for triggering values that are given...
This circuit generates a good-intensity 1 kHz rectangular signal. The circuit is from Electronics Now...