6-8
Installation
Date Code 20000421
SEL-251, -2, -3 Instruction Manual
Caution:
Do not select two baud rates for the same port. This can damage the baud rate
generator.
Password Protection Jumper
Put JMP103 in place to disable password protection. This feature is useful if passwords are not
required or when passwords are forgotten.
OPEN/CLOSE Command Enable Jumper
With jumper JMP104 in place, the OPEN and CLOSE commands are enabled. If you remove
jumper JMP104, OPEN and CLOSE command execution results in the message: "Aborted."
A4 Output Contact Jumper
With jumper JMP3 in the A4 position, the A4 output contact operates per setting A4(2346).
With jumper JMP3 in the ALARM position, the A4 output contact operates with the ALARM
output contact.
Communication Port External Power Jumpers
+5 Vdc power is available from Port 1 and Port 2R to energize external devices. JMP12 must be
bridged in order to route power to the rear ports. Use caution to ensure the dc current require-
ment of the external equipment does not exceed the relay power supply specifications. Route dc
power to the rear ports only when required by your application.
EIA-232 and IRIG-B Installation
The following information contains specific details regarding communications port pinouts.
A pin definition of the 9-pin port connectors and cabling information for the EIA-232 ports
appears in Figure 6.1. The following cable listings show several types of EIA-232 cables. These
and other cables are available from SEL. Cable configuration sheets are also available at no
charge for a large number of devices. Contact the factory for more information.
EIA-232 Cables
Cable 234A
SEL-251
9-Pin *DTE Device
GND
5
TXD
3
RXD
2
CTS
8
5
GND
2
RXD
3
TXD
7
RTS
8
CTS
1
DCD
4
DTR
6
DSR