The Smartphone Alarm will accept up to 20 paired devices that can include a combination of no more than 6
camera PIR's or
video camera PIR's. This alarm includes 5 devices as standard, one of which is a camera. This means you can add an additional 15 devices of which 5 can be cameras.
Adding 11 Door Sensors and 4 Video Cameras will take you up to the maximum of 20 devices.
Jonathan P