Schweitzer Engineering Laboratories SEL-421-4 - Figure 2.19 Major Component Locations on the SEL-421 Main Board

2.18
SEL-421 Relay Instruction Manual Date Code 20171021
Installation
Jumpers
Serial Port Jumpers
Place jumpers on the main board to connect +5 Vdc to Pin 1 of each of the three
rear-panel EIA-232 serial ports. The maximum current available from this Pin 1
source is 0.5 A. The Pin 1 source is useful for powering an external modem.
Figure 2.19 Major Component Locations on the SEL-421 Main Board
J18 or J21
Rear of Relay