This circuit allows the detection of RF signals using the lowest range of direct currents of a common multimeter. Equivalent diodes such as 1N34 can be used. The circuit is assembled in a ballpoint tube.
A simple version of VCO CMOS using 4049 inverters is shown in the figure. This circuit can be...
This simple SCR relaxation oscillator was indicated by a 90s Popular Electronics. The frequency is...
This circuit can be used as an answering password system in a store, office, or other location....