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Simple DIY Cable Continuity TesterHow to useThis simple cable tester can be used to check 2 wire cable such as coax cable, telephone cable, audio cable and etc.Power the circuit using 9V battery.Plug in the cable and push "TEST" button.The dummy resistor is connected to the end of the cable which has 75ohm resistor inside.The tester will show only 3 conditions, "SHORT", "OPEN" and "GOOD".How it worksThe method is to check resistance of the dummy resistor at the "Terminator".The idea is simple.Imagine there is a short circuit cable under testing.The wire will act as nearly zero ohm resistor thus making the voltage divider near the dummy resistor to divide the 9V into 4.5V.Calculate it your self [ ( 1k / ( 1k + 1k ) ) * 9V = 4.5V ].4.5V is below...
