This experimental circuit with Nixie tube was found in the Radio Electronics magazine of March 1969. The circuit serves for demonstrations and also for testing these digital indicator tubes.
Found in a 90s Popular Electronics, this circuit uses two PLL tone recognizers to trigger by touch an...
This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is...
This circuit is from 1995 documentation. In the original, the source is symmetrical at 12 V, but...