This circuit is from Motorola's 1990 Linear Databook. The transistors allow equivalents and the output power depends on the supply voltage. The power supply must be 30 V symmetrical.
This circuit locks when the sensors are opened. The relay can be 6 or 12 V depending on the power...
This is a conventional differentiator configuration with operational amplifier. In principle any...
This circuit should be used with low frequency signals only. The circuit is from a documentation from the...