This circuit is from a 1980's documentation for telecommunications. The circuit is used in SSB and the diodes must be suitable types for the application. The audio input is low impedance.
We found this alarm in a 1992 documentation. The circuit has several timings and the relay can...
Found in English documentation from the 1990s, this circuit can employ equivalent components. The...
This circuit is from a 1990 publication but can still be assembled today with some component...