A small and simple device that sounds a clear, loud alert whenever it receives an incoming call, producing a volume of up to 95dB.The ringer amplifier is very easy to install; simply run the cord that is supplied from your telephone to the ringer amplifier marked \"Tel\" and use the existing telephone cord to plug into the front of the ringer amplifier marked \"Line\". It is powered by the phone system itself so it requires no batteries or additional cables, and it can be switched off when not required without affecting the performance of the phone.