AMX192
AMX192 (often referred to simply as AMX) is an analog lighting communications protocol used to control stage lighting. It was developed by Strand Century in the late 1970s. Originally, AMX192 was only capable of controlling 192 discrete channels of lighting. Later, multiple AMX192 streams were supported by some lighting desks. AMX192 has now all but been replaced in favour of DMX, and is typically only found in legacy hardware.
History
The name AMX192 is derived from an acronym of Analog MultipleXing and the maximum number of controllable lighting channels (192). AMX was indeed developed to address a significant problems in controlling dimmers. In order to send a control signal from a lighting control unit to the dimmer units, for many years, the only method was to provide a dedicated wire from the control unit to each dimmer (analogue control) where the voltage present on the wire was varied by the control unit to set the output level of the dimmer. In the late 1970s the AMX192 serial analogue multiplexing standard was developed in the US, permitting one cable to control several dimmers.
At about the same time, D54 was developed in the United Kingdom, and differed from AMX192 in that it used an embedded clocking scheme. AMX192 used a separate differential clock with a driver circuit similar to RS485, but current limited on each leg with 100Ω resistors.