On 10/04/05 02:44 ET, Ernie Bornn-Gilman said...
RS-232 is indeed limited in its transmission length,
but there is another similar standard meant for
going distances like 500 feet. RS485, RS422,
RS423 result from a google search. I think 485
is the standard you are looking for, and there
are devices that translate from 232 to 485.
Also check
[Link: rs485.com]RS-485 is almost certainly NOT what you are looking to use. RS-422 is balanced RS-232 and will carry data signals up to 4000 feet. Short haul modems could work but I think I would opt for a IP solution as Rick le deuxieum suggested. A device server would work if you don't have one of the big boys specified as a control system. This is not the place to go into all the reasons why 485 is the wrong protocol but keep in mind that RS-485 is one to many while 232 and 422 are 1 to 1 device protocols. Of course, if you have an existing RS-485 network in place ( like Netlinx or Cresnet ) you can take advantage of it and use a propritary breakout box. I recall VUpower informing us that his company subs out its Crestron work. Therefore that is not a likely solution in his case though this may be one of those jobs where Crestron is subed in to the job spec.
Something very important to keep in mind, especially running data signals on different power grids over long distances is to opto-isolate the com ports on each end. If you are using IR I might just stick an extra diode on the wires heading South just for safety. I'd much rather replace an emitter than a com port or IR driver.
The Audio Control will work at least to distances of 1000 feet for audio signals. Someone on this board did it although he also reported that he needed to re-run his cabling as rodents (prairie dogs?) ate through the wires.
Alan
