Ideal for those who have trouble hearing when on the phone, this Phoneplus Phone Volume Booster can increase the listening volume of the user\'s existing telephone by up to 40dB.It is operated by simply using the boost button, and there is also a tone control of plus or minus 6dB for added clarity if needed. This Volume Booster is easily connected into the telephone handset cable and is automatically turned on when the handset is lifted. There is also a headset, or neckloop, socket if required. The Phoneplus Phone Volume Booster is supplied with 4xAA batteries to power it. A telephone is not included.