The SHoW DMX OEM Receiver User’s Manual
Rev 1.1 10/14/08
20 of 27 Pages
RDM System Flow
The SHoW DMX system also functions as an RDM Proxy system, by passing RDM
commands and replies back and forth between any connected RDM controllers and
responders. As with DMX, the principal thing to remember about RDM function is that
the Transmitter and Receiver(s)
replace
DMX cable. The main difference between DMX
and RDM operation is that RDM is a two-way system and so both Transmitters and
Receivers may need to function as wireless broadcasters or receivers of the RDM data.
In RDM mode, the SHoW DMX Transmitter converts incoming RDM commands to a
radio signal and broadcasts them to the SHoW DMX Receiver (or Receivers). The
SHoW DMX Receiver takes the radio broadcast and converts it back into standard RDM
data, then responds to it and/or passes it along to connected RDM responders, collects
any reply data from the RDM Responders, then converts the RDM responses back to a
radio signal which is broadcast back to the Transmitter. The Transmitter converts the
radio signals from the receiver back to wired RDM and sends it back upstream to the
RDM system manager, or may function as the RDM system manager itself. A typical
RDM system diagram is shown in the drawing below.
RECEIVER
DMX 512 CONTROL CABLE
12 ~ 24V
LOAD 1
BATTERY
THREE CH. DIMMER
LOAD 2
LOAD 3
WIRELESS RDM COMMAND
WIRELESS DMX BROADCAST
PERSONAL COMPUTER
ETHERNET
CABLE
for RDM MANAGER
LIGHTING CONSOLE
DMX 512 CONTROL CABLE
TRANSMITTER
Frequency Hopping Spread Spectrum (FHSS) Radio Technology
The SHoW DMX radio utilizes a Frequency Hopping Spread Spectrum broadcast format
in the unlicensed 2.4Ghz Industrial Scientific and Medical (ISM) radio band.
FHSS broadcast format is a highly reliable and robust radio broadcasting technology that
utilizes the entire broadcast spectrum by rapidly
hopping
from channel to channel and
broadcasting briefly on each one. The order that the radio follows to hop from channel
to channel is called the hopping pattern, and transmitters and their receivers must be
synchronized on the same hopping pattern in order to communicate. There are many
channels available in the broadcast spectrum, so the radios can hop in many different
patterns, and there is little chance that FHSS radios operating on different patterns will
