Tsetso's advice worked, though now the headphones don't beep when I get the incoming call. It would be nice if they beeped when a call was ringing in, and then stopped beeping when I answered. As it is, I get no audio notification of an incoming call, or I get beeping all through the call (which the caller can also hear, though not as loud).
(I'm using Plantronics Savi 7xx)