Serial Communication Converters & Adapters Instruction Manual
12
Alpha 6203C. A two-wire system requires two twisted pairs, and a four-
wire system requires three twisted pairs (the extra twisted pair is
needed for the signal ground).
Figure 1 illustrates how to connect a general four-wire network (a four-
wire network actually contains 5 wires).
PDA8485
DO
DO
DI
DI
GND
DO
DO
DI
DI
GND
RS-422/485 DEVICE
Figure 1. General Four-Wire Network Connection
Figure 2 illustrates how to connect a general two-wire network (a two-
wire network actually contains 3 wires). Note that the PDA7485 and
PDA8485 have DIP switches that allow for two-wire connections without
the need to externally wire the DO to the DI and the /DO to the /DI (see
the converter section for complete details).
PDA8485
DATA
DATA
DO
DO
DI
DI
GND
GND
RS-485 DEVICE
Figure 2. General Two-Wire Network Connection
