The Telephone Transmitter from Bellman & Symfon is part of the Visit Smart Home System that helps you to keep tabs on your home. Just plug your landline phone into the phone adaptor attached to the Telephone Transmitter–when there are incoming calls from your landline phone, the Telephone transmitter will send out a radio signal to the Visit Receivers. You will be alerted with loud sounds, bright flashing lights, or vibrations, depending on the Receiver you have. The Telephone Transmitter is a great alerting device to help people with hearing loss, hard of hearing, and deaf to stay in touch with family and friends. The Transmitter also features additional trigger inputs that can connect with optional accessories such as a contact mat, magnetic switch, and mobile phone sensor, etc. to detect different events and alert you.