Principles of Voice & Data
Lesson 4:
Troubleshooting
Bellevue Community College
Bob Young, Instructor
Troubleshooting Terms
Short
A connection between two
wires where no connection is
intended
Troubleshooting Terms
Open
No connection, typically where
there should be one
Troubleshooting Terms
Terminator
A line ending, typically a
connector
Example: RJ-45
Troubleshooting Terms
Cross
Def. 1: two wires are touching ("crossed")
where they shouldn't be
Def. 2: two wires are reversed in a
connector (ex. - Pin 2 wired to Pin 3 and
Pin 3 wired to Pin 2)
Troubleshooting Terms
Roll
Two wires of the same pair
are reversed at opposite
ends of the cable
Important Distinction
Be sure you understand the
difference between a
"crossover cable" and a
"rollover cable"
Troubleshooting Terms
Polarity
Associated with the positive
and negative terminals of the
source DC voltage
Troubleshooting Terms
Split
One wire of one pair is
crossed with a wire from
another pair
Troubleshooting Terms
Line Imbalance
Unequal voltages on the two
wires in a pair. This results in
distortion, loss, and noise.
Troubleshooting Terms
Loopback Testing
Testing from one end a line. A
signal is sent, then "looped
back" and measured at the
same end.
Troubleshooting Terms
End-To-End Testing
Testing from both ends of a
line. A signal is sent from one
end, then measured at the
far end.
Analog
Troubleshooting
Tools
Butt Set
•
•
•
•
•
Telephone Line Test Set
Telephone Lineman's Test Set
Line Test Set
Handset
Lineman's Handset
TS-22 Butt Set
TS-19 Butt Set
TS-22A Data Safe Butt Set
TS-250 ISDN Test Set
TS-1000 ADSL Test Set
Load Coil Detector (Model 88)
TS-100 TDR
Cable Fault Finder
77HP Tone Generator
77M Tone Generator
200EP Probe
(Inductive Amplifier)
200B Probe
(Inductive Amplifier)
TIMS (Transmission
Impairment Measuring Set)
Troubleshooting
Analog Lines
Line Level Test
• Milliwatt test
• Level test
• Loss test
• 1000 Hz tone test
Quiet Termination Test
• Quiet test
• Noise test
Ringback Test
An automated system. The tester
dials a number at the CO, then
hangs up. The CO equipment
then calls the number that the
tester called from.
ANAC
• Automatic Number Announcement
Circuit
• Dial the ANAC number, and a computer
generated voice speaks the number of
the line you're testing
• Often accomplished by Caller ID now
• ANAC works on unlisted numbers
DATU
• Direct Access Testing Unit
• Allows you to do user-controlled
tone generation tests
• See next slide, "DAMT"
DAMT
• Direct Access Mechanized
Testing
• Allows you to do user-controlled
tone generation tests
• See previous slide, "DATU"
Echo Test
• Repeats every tone you
generate
• Useful for verifying that you are
generating valid DTMF tones
Troubleshooting
Digital Lines
Check Clocking #1
• Also called "synchronization"
• On a T1, improper clocking may
produce a "Sync" error light
• On a T1, improper clocking may
produce a high BER (Bit Error Rate)
Check Clocking #2
• On a voice circuit, improper clocking
can be heard on the phone or with a
butt set as clicking sounds
• On a data circuit, improper clocking may
show up as random data loss or data
errors
Bit Error Rate
• Not always related to clocking
• Digital equivalent of signal-to-noise ratio
• S/N ratio can be measured on digital
voice circuits in the analog portion
• BER can be measured on all digital
circuits, whether voice or data
• Causes: line loss, reflection, other
ISDN Troubleshooting #1
• Verify that the SPID is programmed
correctly
• SPID = Service Profile Identifier
• Assigned by the service provider
• Programmed in the ISDN "modem" or
terminal adaptor
ISDN Troubleshooting #2
• Verify that the LDN is programmed
correctly
• LDN = Local Directory Number
• Assigned by the service provider
• Programmed in the ISDN "modem" or
terminal adaptor
ISDN Troubleshooting #3
• Verify that the terminator is
installed
• (Contains two 100 ohm
resistors: pins 4 & 5, pins 3 & 6)
ISDN Troubleshooting #4
• Make sure the proper encoding
format is programmed
• For North America, m-law
• For UK and Europe, a-law
ISDN Terminal Adaptor #1
ISDN Terminal Adaptor #2
ISDN Splitter
ISDN Terminator
Digital
Troubleshooting
Tools
Spectrum Analyzer #1
Spectrum Analyzer #2
TDR
Time Domain Reflectometer
Network Analyzer
BERT
Bit Error Rate Tester
Frame Relay Tester
ISDN Tester
OTDR
Optical Time Domain Reflectometer