This sensitive circuit was found in the June 1995 Electronics Now magazine. R1 can be from 10k to 1M depending on the desired sensitivity. Power is supplied by the relay.
This code switch only activates a relay when the right sequence of buttons is pressed. The circuit...
This circuit detects when there was a power cut, triggering the indicator circuit around it. The...
This circuit is suggested by Texas Instruments allowing the modulation of a transmitter from TTL...