This add-on handset requires the ClearSounds A50 main base unit, sold separately. You may purchase up to 2 handsets for use with each main unit you own. Made especially for those who are hard-of-hearing, the phone has an incoming adjustable volume of up to 50dB with a volume control slide bar, an amplification boost button and vibration for the handset. Extra-Clear Tone Control gives you adjustable, full amplification in both high and low tones. The ringer is an extra-loud 95+dB. Ringer volume control lets you choose off, low, medium or high. A flashing ring indicator is located in the handset to give you extra notice of incoming calls. Caller ID has a 99 name and number storage and the phone book has a 60 name and number storage. Duplex speakerphone lets you talk handsfree. Backlit keypads allows you easy dialing, even in low light situations. Phone also comes with emergency dial buttons, the ability to add a bed shaker and is hearing aid t-coil compatible. 900 Mhz. One year warranty.