Date Code 20011026 Installation 6-9
SEL-321/321-1 Instruction Manual
You must provide power to any modem that you install between the SEL-321 Relay and another
device. You can use the SEL-321 Relay to power some types of modems connected to its rear-
panel ports. The SEL-321 will support modems which accept +5 Vdc power. The total current
drawn by all of the external modems powered by one SEL-321 should not exceed 0.5 A. Some
modems power themselves from the control and data lines. These modems do not require
connection to the +5 Vdc power.
Note: The three rear-panel ports provide +5 Vdc at Pin 1 of their 9-pin connectors. These are
tied to the main board power supply. Use care when connecting to these pins.
Misapplication may result in main board damage.
Telephone Line Communications
A telephone dial-up link is one option for off-site communications with an SEL-321 Relay. Use
a modem to convert from the audio telephone line to an EIA-232 interface on the SEL-321 Relay.
You should use telephone line protection equipment where the line enters the building, to ensure
personnel safety and reduce damage to equipment from ground-potential rise and other hazardous
conditions. Connect the line protection equipment to the modem following standard commercial
telephone wiring standards.
Data Flow Control
All SEL devices, including the SEL-321 Relay, support XON/XOFF software data flow control.
Set RTS/CTS = N to connect an SEL-321 Relay to any SEL device. See the SET P command in
Section 3: Communications for details.
The SEL-321 Relay also supports RTS/CTS hardware data flow control on Port 1 and Port 2.
You should select the RTS/CTS option only if the connected device uses RTS/CTS, and does not
use XON/XOFF flow control. Consult the instruction manual or contact the device vendor to
determine the proper flow control technique for each non-SEL device. If you select RTS/CTS
hardware data flow control, make sure that the cable you are using to connect the device to the
SEL-321 Relay has conductors for RTS/CTS.
Baud Rate
The factory default baud rate for the SEL-321 Relay ports is 2400 baud. You can change the
baud rate, and other port communication parameters, using the SET P command (see Section 3:
Communications). Available baud rates are 300, 1200, 2400, 4800, 9600 and 19200.
To change the communication baud rate, you should change the baud rate on the SEL-321 Relay
first, then change the baud rate setting on the communicating device.
Passwords
Factory-set passwords are:
Level 1 = OTTER (all caps)
Level B = EDITH (all caps)
Level 2 = TAIL (all caps)
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