Interactive systems have become indispensible in the security industry. They allow a control room operator to monitor hundreds of cameras, or a central station operator to monitor thousands of sites.
A control room operator is generally posted on the property and will usually have each camera visible on one or more multi-camera screens. With modern equipment, the operator can bring each camera up full screen, control pan/tilt/zoom cameras, control recording, and interact through speakers/microphones with people at restricted entrances.
A central station operator has similar responsibilities, but on a much larger scale. Cameras, microphones and speakers are placed at a customer's site and connected to a phone line for a dial-up, ISDN, or DSL connection (DSL being best). This allows a central operator to interact with people entering, loitering, or leaving a specific area. The operator is essentially a highly-trained "guard" whose response to any situation is guided by the needs of the customer; monitoring pedestrian entrances, vehicle gates, fast-food restaurants, jewelry stores, convenience markets and other locations which require security but cannot afford to pay an on-site guard.
Since the operator cannot continuously watch thousands of cameras , various methods are used for signalling: intercom buttons, motion detectors, vehicle detectors, hold-up buttons, surveillance buttons, door contacts and video motion detection. If any of these are triggered, the signals are sent to the central station where the camera images will come up automatically on a computer screen. The operator can then make a determination of what to do based on the situation. If it just involves loitering or a verbal confrontation, the operator will "voice down" and instruct the troublemakers to leave. If it is an armed robbery, the operator will immediately call the police and not do anything else to aggravate the situation. Video recorders are used at the business location and at the central station which record everything that happens after the signal is received.