The system consists of a camera unit which is installed overlooking the place to be monitored and an indoor video monitor unit that incorporates an intercom also. When the door bell rings the video unit becomes active enabling the image of the visitor to be seen at the monitor inside. One can also communicate with the visitor through the intercom. The electrically operated door locking system can be used to open the door remotely. The electric locks come with a battery backup protection also, just in case there is a power failure. Otherwise these locks can be manually operated also.
While using the video door phone one has to keep in mind that there is a limited area that can be viewed by the camera. In the Video door-phone, normally the camera is located within the speaker unit for the visitor. This means that camera is at the height of the visitor. Now if someone accompanying the visitor does not stand close to the visitor (or stays low), then you will not be able to know of such a presence or number of visitors.
To get over such a limitation, it is advisable to buy models in which camera can be removed & installed elsewhere (from where there is a better view) or to buy a CCTV camera , monitor (your old TV can be used ) a Doorphone system, separately. The integration of all these will require professional help.
