With this circuit found in an American documentation from 1969 it is possible to vary the selectivity (Q factor) of a tuned circuit. The operational is from that time.
Based on an Analog Devices LTC1540, this circuit consumes only 50 uA, serving to monitor the...
This circuit was found in a 1980s documentation. The diodes may be general purpose diodes such as 1N34...
We found this digital timer circuit in a 1994 publication. The power is supplied by 12 V, which is the...