Connecting The Termination Resistor And Diode; Bypass Diode Connection - Samsung SSA-P400 User Manual

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.
RS-485/
RS-232
Converter
RS-422/
RS-232
Converter

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.
SSA-P400(401)
RS-485
120Ω
Termination Resistors
<Termination Resistor in RS-485 Communication>
TX+
TX-
RS-422
RX+
RX-
120Ω
Termination Resistors
<Termination Resistor in RS-422 Communication>
DC+
DC-
Lock/Alarm
A
RS-485
B
120Ω
120Ω
RX+
RX-
RS-422
TX+
TX-
Cathode Anode
1N4004 ~ 1n4007 or equiv.
SSA-P400(401)
SSA-P400(401)
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