There is no official document published by
PLASA supporting the use of 3 pin
XLR cables. Does it happen? Yes, of course. Personally I don't think it should. People should either use the standards or come together and push for a change. I would not support a change in the standard because I think that separating these cables avoids confusion. I have worked on a number of setups that have faults because of the use of three pin cable as
DMX cable. Most of the time the people who set these networks up don't realize that as the length of your
network increases so does your chance of faults. They usually only by one length of cable, too long, because "What's the problem, it's the same cable that you use for a mic".
ANSI E1.11 Section 7.1.1 through 7.1.2 states the following:
7.1.1 Required
connector
Equipment in this
category shall use 5-pin
XLR connectors with the physical pinout of the 5-pin
XLR in
accordance with Table 3.
Table 3 -
[Omitted in this quote]
7.1.2 Concession for use of an alternate
connector (NCC DMX512-A)
A concession to use an alternate
connector is available only when it is physically impossible to mount a 5-
pin
XLR connector on the product. In such cases all the following additional requirements shall be met :
1) The alternate
connector shall not be any type of
XLR connector.
2) The alternate
connector shall not be any type of
IEC 60603-7 8-position modular
connector
except as allowed in clause 7.3.
3) Provided that all other requirements of this Standard are met, in addition to the declaration in
the equipment
manual, the alternate
connector shall be marked as NCC DMX512-A (Not
Connector Compatible). If such a marking is not physically possible at the
connector, an
appropriate marking shall be made elsewhere on the equipment. The pin numbering on the
alternate
connector should match numbering for the standard 5-Pin
XLR connector.
4) The manufacturer shall make available an
adapter with the appropriate connections to a
standard 5-pin
XLR connector for all
DMX512 ports included in the alternate
connector.
5) The Enhanced Functionality, if applicable, and
ground/isolation declarations shall continue to
be declared for each
DMX512 port.
This means that the three
pin connector can not be used on a cable that claims to be complaint to
ANSI E1.11 or E1.27 for the transport of
DMX signal.
As far as the actual cable that the connectors are attached you should refer to
ANSI E1.27 - 1 and
ANSI E1.27 - 2. I will summarize them here but all documents mentioned in this post are available for free
here. The first of the two standards covers cable for use in
portable applications. "
Portable" is typically taken to mean "on the
road" where the cable will me moved, coiled, bent, or plugged and unplugged frequently. Section 4.3 says:
Portable DMX512 cables shall use twisted pair conductors. Conductors shall be of stranded construction ... Shielding shall be on individual pairs or overall shielding of pairs, or both. The
portable cable itself shall be flexible and rugged enough for the repeated coiling and uncoiling to which it will be subjected.
ANSI E1.27 - 2 covers cable construction standards for permanent installation. The only major difference between this standard and the previous is that the standard for permanent applications allows for the use of cables specified as
EIA Category 5 or higher. The change to allow for
category 5 or higher cable happened after the
PLASA Control Protocols Working Group published a report detailing the testing done to compare Cat 5 cable to the EIA-485 cable specified previously. The report was published in October of 2000. All parts of the report can be found
here and the summery of the report can be found
here (pdf).
I'm not trying to through the
book at someone and criticize them personally for the use of 3 pin
XLR but I am trying to
clear up what the standards actually say and provide some useful links.
At the end of the day the curtain has to open and that sometimes means you have to cut a corner. Each of the standards mentioned contain a subsection labeled "Compliance" in section 1 which states
Compliance with this Standard is strictly voluntary and the responsibility of the manufacturer. Disclosures and
identification or other claims of compliance do not constitute certification or approval by
PLASA.
As a TD, LD, Product Engineer, or Manufacturer you have to decide what the right thing to do is right now. If it's possible to follow the standard you should, but if you need to re-terminate that last
DMX cable 30 minutes before the show starts and all you have are 3 pin connectors and it will work, then I would say that you should use the three
pin connector.
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
For anyone who is looking for supplies to
build cables that match these specifications I have been able to source some components from distributors that I trust.
http://www.amazon.com/dp/B0085X62Z6/?tag=controlbooth-20 ($150)
Female 5 pin XLR
Male 5 pin XLR