Promag TR515 User Manual page 4

The RS485 network is of "bus" type- all TR515s are connected in parallel on
a so-called twisted pair bus. The most suitable cable for the bus is the one
normally used for Ethernet communications (twisted pair Cat. III or V). You only
need to use one twisted pair of wires inside the cable.
Note: depending on the cable type, up to 4 twisted pairs may be available, it
doesn't matter which one you use, just make sure that you are using both wires
of the same wire pair.
To connect the TR515 to the twisted pair bus, cut the RS232 cable supplied
with each TR515 and locate 2 wires inside: Orange and Green. Attach each
wire to one of the wires on the twisted pair bus. Mind the polarity! Orange and
Green wires cannot be switched. It is recommended that you keep the length of
each "bus stem" (i.e. the cable that is used to attach a certain TR515 to the bus)
as short as possible, ideally under 10 cm (see the drawing below).
One side of the bus must be attached to the CON485: Orange connects to
pin #3, Green connects to pin #4.
Another side of the twisted pair bus must be properly terminated. This is
especially important for long buses. Standard termination resistor value is 120
Ohm.
Note: It is not always necessary to have the termination resistor. It
really depends on the actual wiring and connection circumstances.
Before testing the network, make sure that all Terminals and the CON485
are powered and that the CON485's baudrate selector is in the 19200 position
(selector must be set prior to powering the CON485 up).
TR515RX's interface connector pin assignment can be found in Appendix B.
TR515 User's Manual
485-
485+
Blue
Green
2
CON485
<10cm
485+ Green
485- Blue
#4
#3