This circuit was found in a 73 amateur radio magazine from the 90s. An LED extends the scale from 0 to 5 V to 10 to 15 V in this bargraph circuit. Other zener values can be used.
This is the circuit of a hearing aid amplifier manufactured by Sony in the 1960s. The circuit was...
Here we show a configuration in which we have a control voltage applied from a voltage divider, which...
This circuit was found in Motorola's 1968 documentation. The SCRs are then replaceable with...