Specifications

Table Of Contents
ARCnet156
32
6.3 Terminations
At 156 Kbps, a signal reaching the end of an unterminated cable can echo, or reflect back, creating a
distortion in the signal and degrading the quality of the communications. To prevent this, every seg-
ment on the ARC 156 network must have a 120 ohm terminator placed at each end of the segment.
To insert the 120 ohm terminator, make sure the module’s power is turned off and attach the termi-
nator to the CMnet positive and negative terminals. The 120 ohm terminating resistors are included
with the ARC156-KIT.
6.4 Wiring Recommendations
If bare communication wire comes in contact with the cable’s foil shield, drain/shield wire or a metal
surface other than the connector, the module might not communicate. When connecting the wire, fol-
low these guidelines:
When stripping the outer jacket, take care not to nick the inner insulation. The wire’s outer jacket
is brittle enough to work free after being nicked or partially cut. Do not strip more than 1 in.
(25mm) of the outer jacket. See Figure 21.
Figure 21 Stripping an ARC156 wire
Strip about 1/4 in. (6 mm) of the inner insulation. Do not allow more than 1/8 in. (3 mm) bare com-
munication wire to protrude from the connector. See Figure 22.
Figure 22 Screw terminal block connection
Twist the drain or shield wires from both cables together before inserting them in the connector.
Inner
insulation
Outer
jacket
Foil
1 in.
(25mm)
1/4 in.
(6mm)
Correct
Incorrect
Incorrect
No more than 1/8 in. (3mm)
of bare wire