I Hear Weird Noises on my HW261N/HW251N

If a Wideband headset is used with a Wideband base or visa versa.

Because of the extended frequency band used in Wideband products such as the M22 & HW series, it is possible to hear noises produced by the phone system that were not audible before because of the limited frequency response of the original handset or narrowband headset.