This circuit consists of an inverter powered by only 4.5 V. The circuit is from a 1967 Mullard documentation. No information was provided on the transformer winding. Capacitors can be 1.5 nF x 3 kV.
This circuit simulates a resistor controlled by digital signals. We found it in American...
Found in Popular Electronics this circuit will trigger a buzzer if the ignition key is removed...
We find this circuit in documentation from the 1980s. The triac and diac are of conventional types...