Samsung SSA-P401 - Manual (Page 13)

English 13
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.
"
#
A
B
<Termination Resistor in RS-485 Communication>
<Termination Resistor in RS-422 Communication>
RS-485/
RS-232
Converter
120 Ω 120 Ω
Termination Resistors
SSA-P400(401)
120 Ω
RS-485 RS-485
120 Ω
RS-422 RS-422
Termination Resistors
TX+
TX-
RX+
RX-
TX+
TX-
RX+
RX-
RS-422/
RS-232
Converter
SSA-P400(401)
DC+
DC-
Lock/Alarm
Cathode Anode
1N4004 ~ 1n4007 or equiv.
SSA-P400(401)