LSC Lighting Redback Wallmount Operators Manual - Manual (Page 43)

Redback Wallmount Dimmer DMX Explained
Operator Manual V1.0
Page 39
7 DMX Explained
DMX512/1990-A is the industry standard for the transmission of digital control signals
between lighting equipment. It utilises just a single pair of wires on which is transmitted the
level information for the control of up to 512 DMX slots (addresses or channels).
The information for each slot is sent sequentially. The level of slot 1 is transmitted, then the
level of slot 2, then 3, etc. up to a maximum of 512 slots. This stream of data containing
the levels for all 512 DMX slots is repeated a minimum (generally) of 44 times per second.
This provides sufficient updates of channel information for smooth fade transitions.
As the DMX512-A signal contains the level information for all slots, each piece of equipment
needs to be able to read the level(s) of the slots(s) that apply only to that piece of
equipment. To enable this, the Redback dimmer has a “DMX Patch” menu that allows you to
patch (connect) each DMX slot (address) from your lighting controller to a Redback channel
number or to multiple channel numbers.
When good quality data cables are used, DMX512 cable runs may be up to 1,000 metres in
length. When several DMX feeds are required (to feed different locations), DMX512 splitters
must be used. These provides multiple isolated DMX512 feeds.
The Redback uses a high impedance DMX input circuit allowing you to loop the DMX signal
from one Redback to the next. The last Redback in the chain must have the “DMX Terminate
switch” set to TERM to terminate the line.
Note: Do not use unscreened microphone or low speed data cables for DMX. This can cause
problems in the DMX network. Make sure the cable conforms to the EIA485 cable
requirements by providing the following specifications:

Low capacitance

One or more twisted pairs

Foil and braid shielded

Impedance of 85 -150 Ohms, nominally 120 Ohms

22AWG gauge for continuous lengths over 300 metres
7.1 TYPICAL DMX INSTALLATIONS
In the following example, the DMX output signal from the lighting control desk is fed to the
DMX connector of the first Redback dimmer. The DMX cable is then looped to the following
Redback dimmers. The order of the daisy chaining is not important as each Redback
channel can be patched to any DMX slot number. The end of the DMX line is terminated to
prevent the signal reflecting back up the line and causing possible errors.
DMX
Cable
Redback
DMX Slots
61-66
Redback
DMX Slots
49-60
Redback
DMX Slots
25-48
Redback
DMX Slots
1-24
Lighting
Controller
Termination
Switch set
to TERM