W&T 18801, Руководство пользователя

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66
W&T
Interface modules
Termination
All RS485 modes require termination of the bus system with a
termination network. The resistor combination integrated in the
module performs two tasks in RS485 applications:
1. The connected line is terminated corresponding to its
impedance, which prevents signal reflections at the cable end.
2. In the high-impedance phases of bus operation a defined
quiescent state is ensured.
The bus system is allowed to be terminated with the terminati-
on network only in RS485 and RS422 modes, but not in RS232
mode.
Closing DIL switches 6 and 7 on the Interface Module
connects the bus terminals to the following resistance
network:
120
Ω
+5V
SW6
SW7
Data In B
Data In A
330
Ω
330
Ω