This circuit from Motorola is from 1968, appearing elsewhere on this site. The transistors admit equivalent and the relay is of the sensitive type for low voltage, according to the power supply.
We found this circuit in a 90s Popular Electronics. It increases the duration of a pulse in a...
This simple circuit detects when a conductive liquid reaches the sensors. The circuit has no...
This converter or inverter uses components that are still common. The transformer is the type...