Found in an Electronic Design of 1964 this circuit has a control for the frequency and another for the active cycle the signal. The bipolar transistor can be a general-purpose type.
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...