This circuit was obtained from a 1967 General Electric manual. The circuit uses components of the time, but equivalents can be used, for example, a BC547 for the transistor and a TIC106 for the SCR.
This circuit is from an August 1984 Radio Electronics magazine. It monitors the state of a RAM...
In the figure we have the way to obtain an adjustable constant current source of 2 mA. The...
Found in a Maxim publication from the 90s, this circuit generates signals from 10 to 25 kHz with a...