Found in the July 1994 Electronics Now magazine, this circuit drives a relay up to 12 V depending on the power supply. The transistor can be general purpose.
In the figure we have a simple signal tracer circuit to be coupled to the volume control of an AM...
This circuit was found in documentation from the 90s, using components from that time. The...
This circuit, obtained from old documentation, allows the recovery of sulfated batteries. The...