VXi OmniCord-V adapter cable, compatible with all VXi V-Series Headsets. It's a simple to use cable that's compatible with just about all the major brand desk phones. In addition, it has a microphone volume boost for phones with low output.
Audio booster and universal cord for all major desk phones
Three-position compatibility (selectable as 1026v, 1027v, or 1029v)
Eight-position microphone boost if needed.
For more details see VXi OmniCord datasheet