The signal from this transmitter is injected into a cable that you want to follow along a pipeline. Monitoring is done using an ordinary AM receiver out of season.
This sonic, sound or vox switch uses common SCR and transistors can be BC548 or equivalent. The...
This circuit allows you to use a calculator as a timer by directly activating a sum key with...
This circuit is from the time when photos were revealed in darkrooms. We found it in a 1968...