We found this circuit in a publication from the 1980s. Transistors can be replaced by current equivalents. The circuit is for 6 V and the capacitors determine the frequency of the oscillations.
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...