Cable Type; Cable Shielding; Figure A-1: Shielding A Cable - Alpha Microsystems AM-6000 Owner's Manual

Connector Configurations Page A-3
2. Signal conditioning equipment (for example, a "short haul modem") can improve signal quality.

Cable Type

We recommend you use a twisted paired shielded and jacketed cable. The cable should be rated at least
CMP Level 3, but you can use CMP Level 5 cable for lines longer than 100 feet. Most cities require that
any low voltage communication cable have a CMP, Communication cable Plenum rating. This type of
cable should comply with your local fire codes for installation in your facility. Using a high quality
twisted paired, overall shielded cable helps minimize electromagnetic interference. Reducing this
interference protects your system from signal noise. It also protects other devices around your Alpha
Micro computer system (such as a TV or radio) from interference radiated by an improperly shielded
system.
The following section, titled "Cable Shielding," provides instructions on creating an adequately shielded
cable that should provide satisfactory protection from interference. Please see the "Important Note"
above for information on your responsibilities concerning electromagnetic interference.

Cable Shielding

There are different techniques for shielding a terminal or printer cable, but the method we recommend as
best satisfying FCC shielding requirements is to use a metal connector hood that connects to the cable
shield. Alpha Micro has pre-made cables available using this shielding technique.
The shielded cable consists of several layers. On the inside are the colored wires that carry the data
signals. Surrounding these wires is a metal foil covering. On the outside of the foil covering are small,
uncoated, "drain wires." Completely surrounding all of the above elements is the plastic coating that
forms the outside of the cable.

Figure A-1: Shielding a Cable

AM-6000 Computer Owner's Manual, Rev. 00