This circuit was obtained in a 1967 Raytheon manual. The company's component is an optical coupler with a photo-resistor and a lamp. Transistors support equivalents.
In the figure we have a negative power circuit for SCR and unijunction transistor suggested by...
We found this oscillator in a documentation for radio amateurs from the 1970s. The circuit can use...
This 5 V power supply for TTL, Shields and microcontrollers is old, and the components can be...