The resistors balance the cable plant between the receiver and the transmitter on the T-type interface. The resistor is built into the NT1 and can be one of three values, depending on the configuration and the distance from the NT1 to the Integrated Services Digital Network (ISDN) terminal. The resistor value is controlled from the NT1. In some cases, a terminating resistor (TR) adapter is needed and can be placed in the satellite closet or work location.

NOTE:

The 440A4 terminating resistor and 110RA1-12 terminating resistor block are Underwriters Laboratories (UL) listed. Most new installations will be of the 110RA1-12 terminating resistor block. The following installation instructions should be observed and heeded when installing a terminating resistor (TR) or any telephone equipment.

Never install telephone wiring during a lightning storm.

Never install telephone jacks in wet locations unless the jack is specifically designed for wet locations.

Never touch uninsulated wires or terminals unless the telephone line has been disconnected at the network interface.

Use caution when installing or modifying telephone lines.

Terminating Resistor Adapter

Figure 9-17shows an 8-pin 440A4 terminating resistor (TR) adapter. The adapter is three inches long with plugs at both ends and a short cord to connect the 8-conductor jack. When is connected, a small screwdriver is needed for removal.

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R

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9-40Issue 1 September 1995

Page 170
Image 170
AT&T 555-230-894 manual Terminating Resistor Adapter