RJ45-DMXTERM-120 or RJ45-DMXTERM-120-2U is an RJ45 connector plug with a 120 Ohm resistor inside connected to the data lines. Plug this in at the last DMX unit, and the DMX source perceives the cable as endless. Otherwise, reflections are created at the end of the cable, causing problems that are very difficult to find. Avoid this by terminating the end of the cable. is an RJ45 connector plug with a 120 Ohm resistor inside connected to the data lines. Plug this in at the last DMX unit, and the DMX source perceives the cable as endless. Otherwise, reflections are created at the end of the cable, causing problems that are very difficult to find. Avoid this by terminating the end of the cable.