This traditional configuration with the 555 was obtained in an 80s Hands-On Electronics. The relay is of the sensitive type according to the supply voltage.
This 1 A circuit was found in a Philips documentation from 1966. The transistor is of the time,...
This FM transmitter circuit was found in a Japanese publication in 1975. Equivalent transistors can be...
In the figure we have the basic configuration of a 5 V regulator using an operational 741. In this...