This circuit was obtained in an Electronics Now from the 90s. The circuit uses operational amplifiers from the time and the indicator is of the Sonalert type with internal oscillator.
This circuit was obtained in a 1978 English magazine. This adjustable stabilized power source...
This circuit was found in old documentation, but as it uses the 555 it can still be easily...
This timer with field effect transistors was obtained from Fairchild documentation. The times...