Black Box 32144, Manual

Page: 28 / 195

179
APPENDIX C: Connectors, Adapters, and Jumpers
C.2 Jumpers
WARNING
Jumpers should be switched
only by qualified service
personnel.
For most applications, there is no
need to reset the modem’s internal
jumper switches. However, a
jumper switch will have to be reset
if you need to—
Connect frame ground to signal
ground, Switch from A/A1 control
to MI/MIC control, Strap the
modem for use in a DC rack
enclosure, or Change the function
of EIA interface pin 25.
If you need to reset a jumper
switch, refer to the following page
to determine the jumper that
should be switched, where it is
located, and how it should be set.
The jumpers are numbered on the
circuit board; for example, JP4 is
jumper 4. To access the jumpers,
unscrew the four screws on the
bottom of the modem and carefully
lift off the cover.
WARNING
Improper setting of AC and
DC power jumpers could
result in serious damage to
the modem.