This circuit was found in a 90s Popular Electronics. The circuit uses components from that time, intended to receive signals in the range of 150 to 250 kHz.
This simple light relay circuit was found in a 1988 documentation. The base is the operational 741 which has...
This circuit is from an August 1984 Radio Electronics magazine. It monitors the state of a RAM...
This 2005 circuit from a Linear Technology manual makes use of the LTC610HV and an optical coupler that...