NEC UNIVERGE SV9100 System Maintenance Manual page 19

UNIVERGE SV9100 Issue 1.0
B1
Frequency Interference (RFI)
Is interference only on outside calls or anytime
station is off-hook?
Remove one CO line at MDF
Outside calls and test using standard SLT.
RFI Event?
Any off-hook
No
RFI on CO
Check cable for the affected
Lines?
terminal(s).
Yes
More than 1-pair
Twisted
Cable with 1-pair twisted pair
Ground all unused pairs at
Telco.
cable.
MDF.
pair?
No
No
RFI Cleared?
RFI Cleared?
Yes
Yes
End
End
You should investigate the source of the external RFI
System Maintenance Manual 7