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I used plantronics cs540 (they didnt want to spend the money on the savi 740), but I think you will find any with a selector switch will work.The only issue I found with the plantronics cordless headsets is that when the headset is in the base it open circuits and the 5550 thinks there is no headset plugged in (which means you cant change to present without first lifting the headset). I found way around this was to plug a handset into the handset port of the headset base, this was not ideal so i jigged up a plug with resisters to plug into the handset port on the headset base so it always thinks there is something plugged in.