IBM 5500-01E, Operational, Installation, And Maintenance Manual

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The Phases within a twinax cable are generally called Phase B and Phase Y
(or A). The conductor that is Phase B at one end of the cable must also be
Phase B at the other end (for example, the wires must not be crossed). The
twinax cable is normally coded such that one phase is copper colored and the
other phase is tin coated to assist in correct orientation. However, some cables
are not color coded at all.
IBM recommends that the copper conductor is inserted into the plug or socket
hole that has a dot next to it. This is Phase Y (or A). Figure 39 is a view of a
twinax connector, indicating which conductor is phase A. (Phase B is the
other Conductor.)
Figure 39: Twinax Cable Connector
With one of the pins tied to the shield at the far end, measure the pin at the
nearest end. The resistance should be less than 70
W
(if over 70
W
, the phases
are crossed.)
If you have Station Protectors in the line you will not get valid resistance
readings. Either temporarily disconnect the Station Protectors or test the line
beyond the Station Protector. Avoid this procedure if there is a chance of
lightning. There should be common grounding between the station protector,
the utility ground, and all extensive metal components in the vicinity of the
system.
Advanced Troubleshooting
This section is for qualified maintenance personnel who service the 5500
Control Unit and twinax cabling installations. Refer to the Safety Information
Booklet, S021-0030 and review “Safety Information” on page 143 before
continuing.
Required Station Protectors
Station protectors are required for each outdoor or underground cable run.
Only one pair can be installed per twinax run, and they must be installed in
pairs inside the buildings. Locate them where the cable enters or exits the
Phase A
Phase B
Cable Plug
55E1I045