This is an old test circuit for integrated TTL counters, feeding a Nixie tube, common at the time. The circuit is from the 90's, not being given the power supply.
Found in a 1970 EEE, this circuit uses general-purpose transistors of the time. Transistors support...
This simple source using fixed voltage regulators can supply currents up to 1 A at the voltages...
Originally suggested by Harris in the 1990s, this circuit uses an optical tachometer. The circuit is...