Found in American documentation from 1968, this circuit uses both diodes and a neon lamp to generate a 4-step ladder. Observe the signal voltage.
This circuit is from Popular Electronics from October 0, 1981. The diodes can also be 1N4004 and...
This switch or band selector for receivers was found in a Popular Electronics from the 1990s. The...
This circuit, published in 1978, can use any general purpose NPN transistor such as the BC548 and...