As an occasional installer of alarm systems, David covered a lot of ground testing the integrity of the four-conductor cables commonly used as wiring. Each wire has four conductors and must be checked for shorts and opens. To cut down on all of the back and forth, he built a simple voltage divider that sends a different voltage down three of the wires with respect to the fourth one-requiring only a single trip to the panel for each wire. Low resistor values ensure the 9V battery isn't killed if the wires are shorted.
|Nifty 4-Wire Cable Tester Parts List|
|Amt||Part Description||Allied Part #|
|1||Vector Board #8015-1||977-1256|
|1||3M Single Row Female Socket Strip||618-5162|
|1||9V Battery Holder||839-1294|
|1||5.62K 1/4W 1% Resistor||832-6460|
|3||1.0K 1/4S 1% Resistor||832-7950|