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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.
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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.
Butt Set • Telephone Line Test Set • Telephone Lineman's Test Set • Line Test Set • Handset • Lineman's Handset
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
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