An appliance (NetBotz 500/420/320/400/310 series) comes with a door sensor that plugs to Switch Sense port(an audio-style connector). Length of the door sensor depends on the appliance is a 'rack' or 'wall' unit.
A NetBotz rack-mount appliance comes with a 12-ft door sensor; a NetBotz wall-mount appliance comes with a 50-ft door sensor.
There is also DIN-style door sensor (12-ft) available for purchase. It is for used with an external port on a Sensor Pod 120 or a NetBotz appliance.
Door sensor for additional cameras:
A Camera Pod 120 (purchased separately from an appliance) comes with a 50-ft door sensor. However, a CCTV Adaptor Pod 120 does NOT come with a door sensor. Separate purchase is required.