A picture interphone system uses existing an TV and camcorder without any special equipment. The system is able to record a picture of a visitor while the user is not at home or when the user wants to record the picture of the visitor. The camcorder and the TV are turned on by the signal of a switch...http://www.google.de/patents/US5142604?utm_source=gb-gplus-sharePatent US5142604 - System and method for picture interphone using camcorder and TV
