This two-transistor regenerative switch works as an excellent trigger for SCRs and other devices that need sharp pulses. The circuit is from an old documentation.
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....