In more sophisticated systems, there are also features for one-way video communications between selected points. These video devices are usually installed at entry doors to permit the resident to see and speak with a visitor before using a remote lock release to permit entry.
In most systems, all stations can call all other stations. This generally functions in much the same way as stations in a commercial telephone system. When a video station is installed at entry doors, usually only certain stations can receive the video portion of the call.
Generally, combined video intercom systems used in residential applications are interconnected by direct wiring to allow continuous talk paths and transmission of video images. In commercial applications, the video components are separated into intercom and CCTV systems (see other section of this website for more information on commercial intercom and CCTV systems).
Please note that residential intercom system should be chosen with the help of a qualified design and implementation specialist.