This filter for the 300 Hz to 3 kHz range was found in an American documentation from the 90's. The operational amplifier is a double 741.
This circuit doubles the pulse rate produced by a digital TTL circuit. The circuit is from a 1976...
This alarm with automatic shutoff was found in the April 1975 Radio Electronics magazine. The...
This 12 V to 110 V inverter with 100 W was found in a 1977 Signetics manual. The transformer must...