This is a typical point scale or moving bar circuit with the LM3915. We found it in old American documentation. The operational amplifier supports an equivalent modern type.
This commercial transistor radio was manufactured in Japan in the 1960s. The circuit has only 3...
This useful signal injector using two transistor was found in a Radio Electronics Magazine from...
In the figure we have the way to control a flip-flop with the 4069 from positive pulses. The...