C1300
Advanced Circular Chart Recorder
2 Electrical Installation
IM/C1300–MOD
Rev. C
5
2.4 Termination Resistors
For long transmission lines, termination resistors are required on the last slave in the chain and the host computer/computer terminal
– see Fig. 2.3. Under normal operating conditions the resistors are required at the receive inputs only. For 2-wire operation the slave
termination resistor is fitted to the serial module terminal board – see Fig. 2.3A. For 4-wire operation the slave termination resistor is
selected using plug-in links on the serial module – see Fig. 2.3B.
2.5 RS485/422 Standard
The RS485 standard quotes connection of thirty two slaves maximum, to any single driver (computer terminal or host computer); the
RS422 standard quotes connection of up to ten slaves. However, these numbers can be increased if the driver's serial port permits.
Fig. 2.3 Slave Termination Resistors
7 6
12 1
2
5
4
3
6
A 2-wire Operation
120
W
External Termination Resistor see
Notes
Tx+/Rx+
Tx/Rx
B 4-wire Operation
Termination
Resistor
Linked In
see
Notes
1
12
3
10
2
1
Termination
Resistor
Linked Out
3
10
2
1
1
12
PL2
PL2
PL2
2
3
4
5
6
Note.
For 2-wire operation an external 120
resistor must be on the last slave in the chain. The resistor
is fitted across terminals 4 and 5 on the serial module terminal board.
For 4-wire operation the internal termination resistor on the last slave in the chain must be linked in.
