Some of my testing errors with this headset (which has a replaceable battery) appear to be due to the state of charge of the battery. The supplied AAAA battery is marked Alkaline 1.5V. I have been using rechargeable NiMh batteries of the same approximate size. When fully charged these appear to have about 1.35V. This is enough to run the headset but errors increase markedly when down to about 1.30V.