The regular 2.5mm cords will kind of work, but the Plantronics Gold Plug is the best solution!
The Plantronics Gold Plug is no longer on the website.
We can always send the 2.5mm cords for corded headsets as long as we are communicating the gold plug solution to our Customers first!
If we are unable to get the 2.5mm cord to work with the Cisco SPA phone, we will need to get the Customer an amplifier to plug into the handset jack.
Why it does this:
The 2.5mm port on the Cisco SPA phones are shaped a little bit differently than normal 2.5mm ports. Because of this, our Customers may experience one way sound, garbled sound, or no sound at all if the cord gets bumped. Unseating and reseating the cord should temporarily resolve the issue, but it may keep reoccurring due to the shape of the 2.5mm headset jack.