This circuit that generates signals between 1.5 and 2 kHz was found in a documentation from the 90's. The capacitor C1 can be changed to obtain other frequencies.
This circuit is from an August 1984 Radio Electronics magazine. It monitors the state of a RAM...
Analog Devices suggests this circuit in documentation from the 1990s. The circuit is for 75-ohm...
This circuit, which can be built with several CMOS gates, was found in the March 1996 issue of...