RS-485 standard addresses some short coming of the RS-422
standard. The standard supports inexpensive local networks and multidrop
communication links, using the same differential signalling over
twisted pairs as RS-422. The main difference being that in RS-485
drivers use three-state logic allowing the individual transmitters
to deactivate while not transmitting, while RS-422 the transmitter
is always active therefore holding the differential lines. Up to
32 devices can be connected, but with repeaters a network with up
to 256 devices can be achieved. RS-485 can be used in a full-duplex
4-wire mode or half-duplex 2-wire mode. With long wires and high
baud-rates it is recommended that termination resistors are used
at the far ends of the network for signal integrity