The Walker W6B universal compatible amplified handset is designed to work with virtually all telephones (except those with a dial pad in the handset) because power is supplied by batteries (2 AA batteries included). The W6B series provides amplification and noise canceling. The user can adjust incoming signals with up to 22 dB of gain. The user selectable transmitter ensures proper outgoing volume levels. The W6B only works with analog phones (excluding those with a dial pad in the handset).