I have a hs 850 paired to a I-Phone and about half the time when the phone rings neither the phone or the headset will make a noise. I can only tell it's ringing by looking at the phone display. I have tried changing ringers and turning off the vibrate and it does not help. When it is not connected to the earpiece phone works fine.

SOURCE: Motorola H350 - Incoming calls

there is nothing you can do about the delay as it's the time it takes for the bluetooth to send the signal to your earpiece to tell it the call is answered, the only way to stop any delay is to set your phone to auto answer in the bluetooth headphone settings or in the call settings.

SOURCE: H350 HEADSET

you may have the earpiece volume too low, because you will only recieve a bleep when there is an incoming call, not a ringing tone, or just set it to auto answer in the phone settings.

SOURCE: it's paired up with treo, but when treo rings, the headset will not work.

there are known compatability issues with palm treo and blackberry phones when trying to use this type of headset .

I recomend a Plantronics brand headset with your phone.

SOURCE: HS 850 won't go into pairing mode

Usually to solve some pairing problems shut off bluetooth completely(no lights) Push and hold button until bluetooth comes on,flashes then steady light,you may have to hold button for ten seconds or more.Then put phone in pairing mode.