After digging through the net and all my documentation I came up with the following reference in one of the UNIStim release notes.
A constant humming noise is sometime heard through the headset when either the Enhanced USB Headset Adapter or the Mobile USB Headset Adapter is connected to the 1120E, 1140E, 1150E or 1165E IP Deskphone. The humming noise heard within the headset can be corrected by upgrading the Headset Adapter firmware to version 2.00.98 or greater.
The USB Headset Adapter firmware version 2.00.98 is available for download from the “Software Download” link under “Support and Training” on the Nortel website located at: http://support.nortel.com. The firmware is available for the 1120E, 1140E, 1150E and 1165E IP Deskphone models under “Phones, Clients and Accessories” as file Adapter3v2.0098.zip.
To load the version 2.00.98 firmware onto the USB Headset Adapter perform the following procedure:
- Download the firmware file Adapter3v2.0098.zip from the Nortel Technical Support web site
- Load the file Adapter3v2.0098.zip onto a PC
- Uncompress (unzip) the file to obtain Adapter3v2.0098.exe.
- Connect the USB Headset Adapter to the PC
- Start the Adapter3v2.0098.exe application to load the firmware onto the device.
Hopefully this helps someone else out. It took me quite sometime to locate any reference and I had almost given up.