About Us About Us
Products & Services Products & Services
Services for Departments for Faculty and Staff
Services for Residents for Residents
Services for non-UCSB Groups for Non-UCSB Groups
Infrastructure Infrastructure Services
Directories Directories
Reference Information Reference Information
Reference Information About This Site
 

 

Communications Services My Account | Contact Us
  
view site map contact Communications Services staff
  CommServ > Infrastructure > Standards > History > Sample Acceptance Testing Procedure

    The following is a suggested sequence for testing twisted pair cabling installed under the proposed UCSB standards for communications cabling.

    Correct Terminations

  1. Verify that the identification number (label) is identical for both the jacks in the workstation wall plate and in the corresponding patch panel jacks to be tested.
  2. Verify that a mechanically sound connection exists for each wire at each of the attached terminations on an RJ-11 or RJ-45 jack.
  3. Verify correct straight-through correspondence of all four (4) wires at each RJ-11 or RJ-45 termination of the cable.
  4. If a single-end test device is to be used, verify the pin-to-pin continuity of each pair within the loopback plugs to be used at the opposite end.

Continuity

Check for the following.

  • Crossed: One or both wires in a pair cross, or short, with one or both wires in a second pair. Identify by use of third pair individual wire.
  • Ground Fault: One or both wires in a pair read continuity with external ground or shield.
  • Intermittent: A break or "open" which appears and disappears as the wire or connector is flexed. Identify by same method as "open" pairs.
  • Open Pairs: A break or "open" fault appears. Use a split-pair loopback plug or individually use one wire in each of two pairs to determine which individual wire is "open".
  • Reversed: The termination of a wire pair is reversed, e.g. a telephone circuit "tip" at one end appears as "ring" at the opposite end.
  • Short: Continuity between two wires without an external jumper or loopback plug in place.
  • Split: Between two pairs, one wire of one pair is reversed with one wire of the second pair. Identify by use of third pair individual wire.

Signal Loss

This test measures attenuation of the wire by injecting a signal of known strength at one end and measuring the strength of the signal at the opposite end. This measurement over known distance is compared to the manufacturer's design specification for loss over distance (typically xx dB per km).

Signal loss should be measured at multiple defined frequencies and compared with manufacturer's specifications for loss at each of those frequencies.

NOTE: This test should be performed with the full length of cable off of the shipping and/or package reel.

Crosstalk

Near-End Crosstalk (NEXT) is measured to determine a signal-to-noise ratio for a cable run and normally will be a measurement of the noise level in a receive pair generated by an adjacent transmit pair.

A common source of NEXT is the existence of a split pair in which one wire of a transmit pair is reversed with one wire of a receive pair.

Interference

Interference is measured, or identified, as a source of noise external to the twisted pair structure of the cable under evaluation. Typical interference sources include electric motors and flourescent lighting, as well as any high-voltage circuit running parallel to the signal cable path. Increasing the distance between the signal and the electric cables is required. Shielding on the cable, or for the termination may also be required.

Ground Loop

In a large wiring system, with multiple sub-terminals and backboards, a ground loop may be formed by inadvertent use of two ground references for shielding or equipment. Such a group loop may result in both a rise in crosstalk signals or loss of attenuation.

A single grounding system should be established for each building, using a single copper ground rod (8' earth driven) and running a bus circuit (#6 wire) to each closet with a mounted ground bar. All equipment and cable shielding should be grounded as required to this bar.

DCC

University of California Santa Barbara Home Page
Copyright © 2003-2017 The Regents of the University of California, All Rights Reserved
Web contactTerms of UseAccessibilityPrivacy
Last modified: 10/19/2007