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Title: Loud hum when connected to phone.
Review: I have tried 2 phones and still got a loud hum in the phone. I have now tried 3 phone lines. When I contacted Plantronics they sent me a unit marked "Refurb". It still did not work without the buzz. I also noticed if you tap on the case you can hear the tap in the headphone so the unit is harmonic for some reason. Anyway it does not work well and I now I have a Refurb unit I can no longer return to Amazon and get my money back. Beware!
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