The MPX-100 lighting controller generates and receives DMX512 data to aid in testing lighting systems. The unit also serves as a remote focus unit, giving the lighting designer access to all 512 DMX channels from a hand held device. The unit operates on four AA cells. A 3 digit thumbwheel switch selects the DMX channel currently being controlled by the slider. As the channel is changed, the MPX-100 continues to transmit previous channel settings, so an entire stage look can be built if desired. When the channel switch is set to 999, the slider runs all 512 channels up and down. When the channel switch is set to 998, incoming DMX is "scaled" by the slider on the MPX-100, acting like the grand master control on a lighting console. The MPX-100 includes 3 LED indicators. The left LED is lit if DMX is being received. The middle LED varies in brightness according to the incoming DMX. The right LED is lit when the unit is on and flashes when the batteries are low. When DMX is being received (left LED lit), the middle LED varies in brightness according to the level on the DMX channel selected by the channel select switch. If the channel select switch is set to 998 or 999, the middle LED brightness is determined by the highest level of any channel in the received DMX. In addition, when DMX is being received, levels set by the MPX-100 (channel switch set to 1-512) slider are combined with the received DMX using "highest takes precedence. "