This heating element control with up to 3 kW was obtained from an old American documentation. SCRs must be load-compliant, and transistors can be current equivalents.
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....