This simple circuit to monitor the frequency of the power grid uses an analog indicator. The adjustment trimpot can be 4k7 and the indicator is 100 mA full scale.
A simple version of VCO CMOS using 4049 inverters is shown in the figure. This circuit can be...
With this name, the English publication where we found this circuit indicated a sensitive touch...
This circuit was found in a 1986 documentation. The circuit uses 12 V relays and is powered by a...