This circuit is from an old American documentation from the 70s. Transistor 2N3904 can be replaced by BC548. The relay must have 100 mA of maximum current.
This circuit was found in a 1990 Electronics Handbook. The transistors can also be the BC548 and...
Found in a 1967 documentation this circuit can be applied to any operational amplifier. Components...
This simple AM transmitter for very small ranges uses in the original version of the 1970s, a...