Why is the mic "lit" on my NEC Elite 8-Button Display Telephone DTU-8D

In the link

https://www.google.com/search?q=nec+dtu+16d-2+turn+on+voicemail&

Manual

Dtu-16D-2 Tel - NEC Electra Elite IPK II System ... - ManualsLib

https://www.manualslib.com > manual > Nec-Electra-Eli...
NEC Electra Elite IPK II Manual Online: Dtu-16D-2 Tel. This digital Multiline Terminal has 16 programmable line keys (each with a 2-color LED), ...

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  NEC 16D and 8D Quick Start User Manual - ManualsLib

  https://www.manualslib.com > ... > Telephone
  View and Download NEC 16D and 8D quick start user manual online. Multiline Telephone. 16D and 8D telephone pdf manual download. Also for: Dth-32d, Dth-16d, ...
  
  

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Standard codes run from 50 to 59. Internal 1,2,3,all, external 1,2,3, all, all internal and external. That's if your codes are at default, and your system is a Pro II, Elite, or IPK. Those phones work on about 8 NEC systems.

Consult the owner manual or if do not have Google the model number for manual. That info has to be in the owner manual--last resort call the customer service for the unit.

Unplug the line cord. While holding down the * and # keys, plug the line cord back in. Release the * and # keys.

Follow the directions on-screen, which will test all display modes, buttons, and sounds for both red and green colored LEDs.

If the feature button continues to flash, press it and then lift the handset and hang up.

Try adjusting the display by using the arrow keys on the bottom right of the phone. The phone must be idle to do this.

Press function button than 1 or feature button than 1

You need to press feature than the number 1 to turn on your mic. You can find support and get anything you may need from ldtsnj.com

Chance's are it's a bad hand set, Swap with another to see if problem follows it. if it dose, replace it.
Richard

Press Feature 1 That will turn the mic off, or on.

For the DTU phone on an NEC Elite system:
Memory Block 4-12
put in the port number and the Lkey of the extension you want to make a headset key.
Programmin on a 16button phone, Lkey 11 needs to be lit and will display H SET to verify.

For the DTP phone, it is generally on an NEC 2000, which is entirely different.