Any 2.5mm headset or headset adapter should be compatible. You can also use most headset adpaters with a Handset lifter. Plantronics and Cisco have worked together to offer a more seemless solution. Cisco has incorporated a built-in amplifier in the headset port, this eliminates the need for an external amplifier and allows for noise-cancelling headsets. All PLANTRONICS H-SERIES HEADSETS are compatible if they come with a 2.5mm plug or you can also use a 2.5mm to Direct connect cable (model 64279-02 or 70765-01)for use with direct connect style headset.