Ref: 09930006
Title: IBM Cabling System Type 3 Media Specification
date: 12/20/89

Copyright 3Com Corporation, 1991.  All rights reserved.

For IBM or 3Com token ring networks operating on telephone twisted
pair, IBM recommends using telephone cable that meets the IBM
Cabling System Type 3 Media Specification.  A network designer
can help you determine whether or not your present cabling meets these
specifications:

1.  #22 or 24 AWG (American Wire Gauge)

2.  Solid copper twisted pairs, with at least two twists per foot

3.  A maximum of 28.6 ohms DC resistance per 305 meters (1000 feet)

4.  Characteristic impedance:

    -  90 to 120 ohms at 256 kHz
    -  87 to 117.5 ohms at 512 kHz
    -  85 to 114 ohms at 772 kHz
    -  84 to 113 ohms at 1000 kHz

5.  Maximum attenuation per 305 meters (1000 feet):

    -  4.00 dB at 256 kHz
    -  5.66 dB at 512 kHz
    -  6.73 dB at 772 kHz
    -  8.00 dB at 1000 kHz


In addition, all Type 3 specified media must meet at least
one of the following industry specifications:

    -  ANSI/ICEA S-80-576-1983
    -  REA PE-71
    -  Bell Systems 48007


