Expand your IS7121 cordless digital answering system with this accessory video doorbell. Like Caller ID for your front porch, it allows you to screen visitors before answering the door, without worry of being seen. The system automatically snaps a photo and sends it to the handset when visitors ring the doorbell. You can then stream video, audio or both with just two buttons. View a snapshot or stream video. Utilizing the latest available frequency band, this interference-free technology provides superior voice and sound quality and higher protection against eavesdropping then 2.4GHz and 5.8GHz phone systems. Length: 2 3/5"; Width: 3 1/2"; Height: 7 4/5".