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Off-premises connections
Issue 3 January 2008 95
The 4C3S-75 may be used only with TN754B Digital Line circuit packs. Table 16: Digital Voice
Circuit Protectors lists the approved protectors.
When possible, all new and reused wiring installations should use blocks that accept the
standard 5-pin plug-in 4C3S-75 protector. However, there are reused wiring installations where
this may not be cost effective. For these installations, the ITW Linx protector may be installed.
An example of this is where screw-type carbon block protectors—or other non–plug-compatible
types—are in place and it is too costly to reterminate the outside plant cable on a 5-pin
mounting block for only a few out-of-building terminals.
Installing the ITW Linx Enhanced Protector
The ITW Linx Enhanced Protector can be installed in series with existing primary protection.
The ITW Linx Enhanced Protector mounts directly on connecting blocks and requires a
separate ground bar.
Installing the 4C3S-75 Enhanced Protector
The 4C3S-75 protector cannot be installed in series with other types of primary protection. It
must be installed as the only protection on the line entering the building. For the 4C3S-75
protector, there are a variety of 25-, 50-, and 100-pair protector panels equipped with 110-type
connecting blocks and/or RJ21X connectors.
Installing the data link protector
The maximum range for out-of-building digital telephones is 3400 feet when using 24 AWG (#5)
(0.5 square millimeters) wire and 2,200 feet (670 meters) when using 26 AWG (#4) (0.4 square
millimeters) wire. The range can be extended to 5,000 feet (1,524 meters) using 24 AWG (#5)
wire or 4,000 feet (1,220 meters) using 26 AWG (#4) wire with the use of a data link protector.
The protector is an isolating transformer used to remove phantom power on the media gateway
side and re-introduce it on the terminal side.
When a protector is used, the telephone must be locally powered by an external power supply
or through the AC power cord provided with some telephones. The protector is installed on the
equipment side of the protection in both buildings.
Table 16: Digital Voice Circuit Protectors
Circuit Pack Enhanced Primary Protector
(With Sneak Current Protection)
TN754B all vintages 4C3S-75 or ITW Linx
TN2181 all vintages 4C3S-75 or ITW Linx
TN2224CP all
vintages
4C3S-75 or ITW Linx