This circuit activates a relay after a time given by C1 and R1. The circuit is from a Radio Electronics from December 1974. The relay voltage is the same as that used in the power supply.
This circuit uses two Raytheon RC4558 operational amplifiers that are similar to the 741. The...
This small stereo amplifier for headphones was found in a documentation on integrated circuits from...
This is a MOSFET version of a grid dip meter for frequencies between 1.8 MHz and 150 MHz,...