Using a 4046 PLL this circuit generates rectangular signals in three wavebands that depend on the capacitors used. The circuit is from a Radio Electronics from December 1989.
This is the basic full-scale circuit of an LM3914 for voltage measurement or voltage triggering and...
This water level control circuit was found in a 1980s documentation. The circuit uses a capacity...
The basis of this circuit is an LM380 that drives a speaker that emits sound when moisture is...