ISDN Line Termination
Determining Termination Requirements
Termination requirements vary depending on the number of devices connected to an external NT1 and the distance between these devices and the NT1.
Single ISDN device
If the DIVA T/A is the only device connected to the external NT1, determine the length of the cable linking the two devices then follow the instructions below.
If the cable is longer than 75 meters (250 feet):
•Connect the included terminating resistor; or,
set the DIV AT/A 100 ohm switch to the ON position.
•Set the NT1 to provide 100 ohms of resistance. Consult the manual provided with the NT1 for more detailed instructions. Note that some NT1s do not support connections over 75 meters (250 feet). Check your user documentation to determine the distance supported.
If the cable is shorter than 75 meters (250 feet):
•Do not connect the included terminating resistor; or
set the DIV AT/A 100 ohm switch to the OFF position (this is the default).
•Set the NT1 to provide 50 ohms of resistance. Consult the manual provided with the NT1 for more detailed instructions.
Multiple ISDN devices
If the NT1 is connected to more that one ISDN device, determine the length of cable connecting the DIVA T/A to the NT1 then follow the instructions below.
If the cable is longer than 75 meters (250 feet):
•Connect the included terminating resistor; or,
set the DIV AT/A 100 ohm switch to the ON position.
•Set the other ISDN devices to 100 ohms of resistance. Consult the manuals provided with these devices for more detailed instructions.
•Set the NT1 to no termination. Consult the manual provided with the NT1 for more detailed instructions. Note that some NT1s do not support connections over 75 meters (250 feet). Check your user documentation to determine the distance supported.
If the cable is shorter than 75 meters (250 feet):
•Do not connect the included terminating resistor; or,
set the DIV AT/A 100 ohm switch to the OFF position (this is the default).
•Set the other ISDN devices to no termination. Consult the manuals provided with these devices for more detailed instructions.
•Set the NT1 to provide 50 ohms of resistance. Consult the manual provided with the NT1 for more detailed instructions.
