The time of this timer depends on C1. The circuit was found in the July 1994 Electronics Now magazine. The supply voltage depends on the relay and can go up to 12 V.
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...