This circuit was found in a 90’s EDN. The components used are still common and the sensors can have their quantity increased. The supply voltage is according to the relay.
This circuit is intended to trigger an alarm when the input voltage exceeds one value and to...
This circuit, found in a 1986 documentation, uses an optical sensor to count pulses and, in its...
This circuit was found in Delco documentation from 1966. The components are from that time....