https://www.headset.com/sennheiser-electronic-hook-switch-ehs-adapter-cehs-dhsg-for-aastra-phones.html
Sennheiser Electronic Hook Switch (EHS) Adapter #CEHS-DHSG for Aastra Phones
Use your Sennheiser wireless headset system with the CEHS-DHSG electronic hook switch adapter to answer calls and end calls remotely from your Aastra...
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