This 10-minute timer was found in the July 1994 Radio Electronics magazine. The relay must be sensitive to the supply voltage used. The capacitors determine time ranges.
This instrumentation amplifier with differential inputs was found in documentation from the 90s....
This circuit is from a Radio Electronics magazine from December 1958. The indicator instrument is analog...
Found in a 90s 303 Circuits, this circuit has an output power of 100 mW. L1 consists of 890 turns...