I realized after researching it that my Plantronics CS50 headset needed a new battery because it was beeping every ten seconds. It was hard to tell whether it was one or two beeps, but since I was not out-of-range I realized it was a low battery. If you desire a copy of the owner's manual, email me and I will send it to you.This battery was much cheaper than buying a replacement battery through Plantronics, and it is exactly the same model and type. It was a headache trying to get the headset battery cover off without breaking it (cheap plastic), but in the end everything is working fine and I am very happy.