I'm assuming you are using a Plantronics HL10 handset lifter. The lifer is what notifies your headset that it has an incoming call. Try turning the ringer volume up on your phone first and see if that solves the problem. If that does not help, it could be the sensor on the lifter is going out. This could be causing a delay in the response time. The lifter ships with a ring detector that has a 2.5mm jack on one end and a small round microphone on the other end. You could try plugging this into the back of the lifter and setting the microphone next to where the lifter is mounted on your phone. This might help in picking up the sound of the phones ring tones. If that doesn't help you might consider replacing the lifter.
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I'm assuming you are using a Plantronics HL10 handset lifter. The lifer is what notifies your headset that it has an incoming call. Try turning the ringer volume up on your phone first and see if that solves the problem. If that does not help, it could be the sensor on the lifter is going out. This could be causing a delay in the response time. The lifter ships with a ring detector that has a 2.5mm jack on one end and a small round microphone on the other end. You could try plugging this into the back of the lifter and setting the microphone next to where the lifter is mounted on your phone. This might help in picking up the sound of the phones ring tones. If that doesn't help you might consider replacing the lifter.
Good luck from Headsets Direct!