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3.11.3 RS485 network topology
Note:
In the picture above, the general network topology of RS485 is shown. N nodes are connected in a multipoint RS485
network. A termination resistance is necessary on both ends of the line to eliminate reflections. Use 120Ω resistors (R)
on both ends. The RS485 network must be designed as one line with multiple drops, not as a star.
3.11.4 Connection cable drawing
Half duplex
T+
120Ω
T-
R+
R-
HOST
Full duplex
T+
T-
R+
120 Ω
R
R-
HOST
VAT Vakuumventile AG, CH-9469 Haag, Switzerland
Tel +41 81 771 61 61 Fax +41 81 771 48 30 CH@vatvalve.com www.vatvalve.com
Installation, Operating & Maintenance Instructions
Series 612 DN 40 (I.D. 1.5"), RS485
R
R
Twisted pair
cable
Twisted pair
cable
Twisted pair
cable
11
T+
120Ω
24
T-
12
R+
13
R-
Valve
12
R+
120Ω
R
13
R-
11
T+
24
T-
Valve
Wiring:
T+
to
T+
T-
to
T-
Wiring:
T+
to
R+
T-
to
R-
R+
to
T+
R-
to
T-
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2011-07-07
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