Sorry Zulma,
We forgot to do three things for correct install the 8510T:
1. Read the DEFINITY EnterpriseCommunicationsServerandSystem75andSystem85
Terminals and Adjuncts Reference 555-015-201
Issue 11
2. Check what power type you are going to use? Here is Installation docs:
The 8510T can receive power from the switch or from an auxiliary power supply.
NOTE:
A voice/data set should be auxiliary powered only.
The installer can select the type of power used by placing the two power jumpers
over the correct set of pins.
The power option jumpers are located at the bottom center of the terminal. On the
right side of the pins, on the plastic housing, you will see the label POWER and a
diagram of the correct settings. The jumpers are labeled PHAN (phantom power)
and AUX (auxiliary power). The terminal is shipped in the AUX position. You must
verify that the jumper settings are set correctly for your configuration.
3. Looks like We should use SPID in station config - in that case you have to set MIM-y
and set SPID - to some value (for example extension number). Then we see into
the installation manual procedure:
The Service Profiler ID (SPID)
When ISDN terminals are initially installed, a unique SPID number must be
entered into the terminal. This number identifies the terminal to the network.
Usually, the system manager provides the SPID for each terminal in the system.
Use the following procedure for entering the SPID in an ISDN 8510T terminal.
1. Press and then press .
2. Dial the numbers, “43” (ID).
3. Press on the dial pad.
4. Enter digits from the dial pad for a new SPID number. If, at any point, you
make a mistake, press to erase the number and re-enter the SPID.
5. When the SPID number is correct, press on the dial pad to save the
new SPID in the terminal.
Menu Mute
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Sorry I did so 8510 installation two-three years ago - it's hard to remember the little things

.