This circuit was found in documentation from the 90s. The transistors can be general-purpose equivalents. The circuit has two versions, one that drives LEDs and another that drives a relay as a load.
This game was found in an old Popular Electronics. The unijunction transistor can be 2N2646. The...
This circuit interrupts the power supply when grounding is missing. The circuit is from an old...
In figure 1 we have a circuit that turns on after a certain time and then turns off, also after a...