This protective circuit for power lines was found in a Radio Electronics from November 1957. The transistor used can be any general-purpose transistor such as the CK722.
In the figure we have a simple way to obtain (almost) sinusoidal signals from an integrated...
This circuit, from a 1973 publication, locks the relay when the light that falls on the LDR is cut...
This transistorized receiver was manufactured in the 1960s and distributed worldwide. The diagram is...