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10_ installation and external connection
installation and external connection
CONNECTING THE TERMINATION RESISTOR AND DIODE
Termination Resistor
A resistor is inserted for matching the line’s impedance to prevent distortion and reduction in RS-422 or RS-485
long distance data communications, which is referred to as termination resistor.
Note that termination resistors of lower than 90 are not allowed, neither more than one termination resistor is
accepted for the communications system.
Bypass Diode Connection
If you connected an inductor (door lock or alarm device) to the output relay, there should occur a voltage surge
while the inductor was between turning on and turning off. If you do not connect a bypass diode to the relay, the
voltage surge will cause damage to the electric circuit of the controller. To reduce this surge, it is recommended to
connect a bypass diode to the relay.
DC+
DC-
Lock/Alarm
SSA-P102
1N4004 ~ 1n4007 or equiv.
Cathode Anode
"
#
A
B
120Ω
120Ω
120Ω
120Ω
RX+
RX-
TX+
TX-
RX+
RX-
TX+
TX-
RS-485/RS-232
Converter
Termination Resistors
Last SSA-P102
RS-485 RS-485
RS-485/RS-232
Converter
Termination Resistors
RS-422 RS-422
Last SSA-P102
<Termination Resistor in RS-485 Communication>
<Termination Resistor in RS-422 Communication>