This analog telephone line extension circuit monitors when the line is in use. We found it in the November 1996 Electronics Now magazine.
This simple circuit controls the signal amplitude through a photoresistor optical coupler. The...
In the figure we have the way to obtain the Exclusive-OR function with 1 transistor. The circuit...
This circuit uses as an indicator a common micrometer type VU with 200 uA of full-scale current. The...