Found in documentation from the 90s, this circuit triggers a relay with inductive signals applied to a link. The sensitivity depends on the frequency and the power supply depends on the relay used.
This filter is suggested by the Texas Instruments Linear Circuits Applications, 1986 edition. The...
This CMOS circuit was obtained in a 1980s documentation. The circuit has a 10-second time delay...
This circuit consists of a switched mixer with digital touch control. The circuit was found in old...