The overshoots from improper termination will have
voltage maximums and minimums at periodic points along the
line. If a maximum happens to land near where a
fixture is, then it causes interference and poor decoding. This is basic "transmission
line" theory. It's just luck of the draw whether an unterminated
DMX system behaves or acts up, and which
fixture will have problems isn't intuitively predictable. The same is true when cable of the wrong
impedance is used, or if one side of the balanced pair is open at some
point. Termination, proper cable type, and
continuity checks are the key to reliable
DMX operation.
