RS-485 and You!

RS-485 and You!

For most fire alarm system installations the job relies heavily on your knowledge of low voltage wiring.  With the changes to NFPA-72 in 2010, the use of Mass Notification Systems have become extremely common. You will find these systems in schools, colleges, and industrial facilities. To properly utilize these systems, including Light Engineered Displays product line,  Visual MNS,  you will need to be familiar with RS-485.

Most assume that because this is a system that ties in with the Fire Alarm System that it relies on low voltage rules to operate. This is a incorrect assumption! RS-485 (also know and TIA-485 (-A) or EIA-485) is first and foremost a data carrying system. This means that different rules apply to it installation, use, and capabilities than standard low voltage.  With our systems we recommend the following for best results.

  • Stranded wire of 24-22 AWG.
  • All wire routing and wire connections are to be “daisy-chained” and not T-tapped. This will cause commuinication issues if not followed.
  • Do not combine RS-485 in conduit with any other AC circuits.
  • Have no more than 30 signs on a data loop.
  • Do not exceed 4000′ per loop at a 9600 baud rate.

These recommendations come from the nature of RS-485. Please see these videos for more detailed information on the nature of RS-485.

Texas Instruments

Analog Devices

If you have any other questions about our lines of Visual MNS please refer to our FAQ page and PDF library for product information.