User's Manual

Introduction
C-6 apC/8X Technical Manual
Note: Although the maximum wire length for an RS-485 connection is 4000
ft., the power to operate an RM-4 must be equal to or greater than 7.5 volts.
Therefore, the minimum power requirements may impact the “maximum”
wire length. For example:
 1 RM at 4000 ft. = 3.516 volt drop using 18 gauge.
12 VDC - 3.512 = 8.488 volts (OK - Sufficient power for an RM-4).
 1 RM at 4000 ft. = 9.36 volt drop using 22 gauge
12 VDC - 9.36 = 2.64 volts (Not OK - Insufficient power for an RM-4).
 1 RM at 1932 ft. = 4.5 volt drop using 22 gauge.
12 VDC - 4.5 = 7.5 volts (OK - Sufficient power for an RM-4)