Found in a 1969 British publication, this circuit uses a regenerative switch with two transistors to produce pulses that depend on C1. The relay must be in accordance with the supply voltage.
This circuit detects the presence of a pilot flame in heating systems by the presence of infrared...
In the figure we have a circuit that uses unusual components, being indicated for low frequency...
Found in older Signetics documentation, this circuit generates signals from 30 Hz to 25 kHz....