This circuit was found in a 1975 documentation. Current general-purpose transistors can be used, and the power is supplied with relatively high voltage. The gain is 30 dB.
When the sensor X1 is opened, the relay is energized. When waiting, the current drained is very...
Based on the LF256 operational amplifier, this circuit was found in the September 1989 issue of...
This circuit was found in a 1968’s Motorola documentation. The transistor is from that time. The...