Product manual

PX Range Product Manual Version 2.3 © Copyright Brainboxes Limited 2013 Page 26 of 45
RS-422 Standard
The RS-422 standard defines a serial communications standard. RS-422 is a high speed and/or long
distance data transmission. Each signal is carried by a pair of wires and is thus a differential data
transmission system. Over distances up to 40 feet the maximum data rate is 10 Megabits per second, and
for distances up to 4000 feet the maximum data rate is 100 Kilobytes per second. A 120-Ohm resistor should
be used to terminate the receiving end of the line. It is generally used between one transmitter receiver pair
to ONLY one other transmitter receiver pair, but each output can drive up to 10 receivers.
RS-422 Standard -1 Driver up to 10 Receivers
Line Length Max Data Rate
40 Feet = 12m 10 Mbits/sec
400 Feet = 122m 1 Mbits/sec
4000 Feet = 1219m 100 Kbits/sec
RS-485 Standard
The RS-485 standard is similar to the RS-422 standard upon which it is based. The main difference is that
up to 32 transmitter receiver pairs may be present on the line at one time. A 120-Ohm resistor should be
used to terminate either end of the main line. If more than one device may transmit data, the RTS line is
used as transmit enable signal, so preventing contention between talkers.
RS-485 Standard - Up to 32 Driver/Receiver Pairs
Line Length Max Data Rate
40 Feet = 12m 10 Mbits/sec
400 Feet = 122m 1 Mbits/sec
4000 Feet = 1219m 100 Kbits/sec