This circuit activates a buzzer when the voltage applied to the input falls below a preset value in R1. The circuit is from an 80's American documentation.
Using a 741 op-amp this circuit high-pass to 10 kHz was found in the February 1995 issue of...
Found in 1965 General Electric documentation this circuit applies to a LASCR used as an optical...
Using transistors and lamps, this simple circuit was found in Popular Electronics. The circuit can...