Compatible with Dogtra Training Collars: 175NCP (S/N less than 103471), 200NCP (S/N less than 111361), 202NCP (S/N less than 101961)/plus 3-3 splitter 1800NC (S/N less than 100121), 1802NC (S/N less than 100101)/plus 3-3 splitter, 1803NC (S/N less than 100101)/plus a 3-3 splitter, 1804NC (S/N less than 100126)/plus 2 of 3-3 splitters