Quaddrix QT-220EX, Руководство пользователя

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3-2 The connection of 120 ohm termination resistor: The termination resistor is
ready on the Protocol PCB. There are two kinds of connections. Refer to the
Protocol PCB jumper setting form for more details.
1) The Picture shows the factory default connection. The jumper is seated on Pin2 &
Pin3 and the termination resistor is not connected.
2) When connecting the 120 ohm termination resistor, the user should pull out the
protocol PCB and plug the jumper on Pin1 & Pin2. Install the PCB back and the
termination resistor is connected.
4. Problems in practical connection
In some circumstances the user may want to adopt a star configuration. For this,
the termination resistors must be connected to the two equipments that are
furthest away from each other, for example, equipment #1 and #15 in the picture
below.
As the star configuration is not in conformity with the requirements of RS485
standards, problems such as signal reflections, lower anti-interference performance
arise when the cable’s length increases along the connection. Also, the reliability of
control signals is decreased with the phenomena that the dome does not respond to
or just responds at intervals to the controller, or is operating continually without
stopping.