A DMX signal should be terminated by the use of a DMX Terminator.

A terminator consists of a 120Ohm, 1/2Watt resistor soldered between pins 2+3 of a 5-pin male XLR. This resistor gives the impression to the transmitting device that the cable is infinite in length, and therefore the signal from the transmitter does not reflect back down the cable.

Some modern DMX devices automatically terminate the signal, negating the need for a terminator - an example of this is the Zero 88 Betapack 3.

A circuit diagram of a DMX terminator (left) and a simple DMX tester (right):

Usage

DMX circuits should always be terminated. It is often claimed that DMX devices work without termination, however this is generally due to good fortune rather than good design; in order to ensure a reliable system, the circuit should be terminated. If the addition of a terminator causes problems in your chain, it is likely down to poor quality DMX Cable. Due to the nature of the DMX protocol, the devices are very sensitive to the quality of the cable and connectors, and misuse of this equipment can cause problems.

See Also

• DMX
• DMX Cable
• DMX Tester
• Tools FAQ