Ref: 09930015
Title: Finding Environmental Problems with Type 3 Cabling
date: 7/20/90

Copyright 3Com Corporation, 1991.  All rights reserved.

The following procedure can be used to identify environmental problems with
Type 3 cabling.  Use this procedure only when other procedures have failed
to isolate the problem.

1.   Verify that the system configuration matches the paper records for
your network and building wiring.

2.   Verify that the maximum allowable lobe length has not been
violated.

The resistance measured across the modular telephone jack pins 2 to 4 and 3
to 5 should not exceed 30 ohms for lobes connected to single-wiring-closet
networks or 15 ohms for lobes connected to multiple-wiring-closet networks.

3.   Verify that the cables are separated from sources of electromagnetic
and radio frequency interference.

4.   Verify the integrity of the AC power grounding system for the
building.  Have a qualified person do the following:

a.  Verify the proper grounding of the power distribution
transformer (the connection of the secondary neutral to
power and building ground).

b.  Verify the correct wiring and grounding of the office
AC power receptacles serving the attaching devices of
the system.

5.   For each segment of the data path, perform the "Ground
Potential Difference and Ground Path Resistance Measurement"
procedure in the IBM Cabling System Planning and
Installation Guide.  If the readings exceed the specified
values, contact the responsible party to make the necessary
corrections.  Retest to verify that the ground potential
difference is within the specified limits.

6.   If any change was made to the cabling or grounding as a
result of measurements in step 5, determine if the problem
has been resolved before proceeding.

7.   If the problem persists, perform the "Measuring Ground
Potential Difference" described in the IBM Cabling System
Planning and Installation Guide.

The operational ground potential difference measurement is a
closed-loop measurement that measures the amount of
potential seen at the input of the attaching device.  This
could be different from that measured open-circuit, as in
step 5.

The operational ground potential differences reading at any
device must not exceed 1.0 volt AC.
