This is a funky one!
This is only used in banks! The picture below is what their Customers see when they pull up to the banks drive through.
Description: The VAT 23GX is the best retrofit solution for remote retail banking, featuring an updated appearance, improved accessibility and audio/video capabilities.
Our Customer is in the bank is plugging their headset into some sort of switchboard system. (We were not able to get exactly what the Customer was plugging into).
Using an OfficeRunner we know the Customer was on phone mode, connector cord was going into the only port in their system, and compat on B. As soon as they turn on their headset they get audio.
Confirmed it works with:
AT&T Marathon, use base jack cord and set to lifter mode.