Hardwired versus wireless systems
Traditionally, camera systems have cabling that runs directly between the camera and the recording mechanism (or viewing monitor). These hardwired runs are usually recommended by manufacturers to not exceed 500-1,000 feet, using RG-59 coaxial cable. Signal equalizers/amplifiers will be required to compensate for signal loss if distances become much greater than 1,000 feet. See exhibit 2.7 for typical transmitting distances.
For exterior applications, cabling for camera systems should be placed within a watertight conduit. Underground cabling should be buried below the frostline or a minimum of 24 inches deep. Direct buried cables (without conduit) are subject to damage by rodents (if no rodent shield is provided), accidental digging, and intentional tampering. Above-ground cabling that is not in a conduit is very susceptible to tampering, as well as environmental degradation. With coaxial cable runs, ground loops (in video applications, this is a current flowing along the shield of the coaxial cable due to a voltage difference in the ground between the ends of the cable) and interference from radio frequencies (RF) or other signals must be considered. Coaxial cables should not be run next to, or parallel with, power lines over long distances. Equipment, such as hum transformers and electronic video clamps, is available in instances where interference is a problem.
With exterior coaxial cable runs, close lightning strikes can induce voltage surges on the cable that can damage equipment on both ends. To protect equipment, surge protectors are installed at both ends of the cable run.
Fiber optic cabling is an excellent alternative to coaxial cable. With fiber optics, there are no concerns with noise, RF interference, ground loops, or voltage surges. Fiber optic systems require a transmitter at the camera end and a receiver at the monitoring end. Fiber optic systems are more costly than coaxial cable systems for short runs but become more cost effective with longer cable runs (greater than 3,000 feet). Installation of fiber optics is also more expensive, requiring trained and experienced installers and specialized tools for handling and connecting.
For interior applications, cabling for hardwired camera systems should be placed within a metal conduit if it is exposed or accessible by building occupants, including maintenance staff. A good example of this is cabling run above loose/replaceable ceiling tiles.
Short-distance, low-power RF wireless camera systems for video signal transmission are becoming more popular. (Wiring is still required for power.) A transmitter is required at the camera, as well as a receiver at the recording end. This will add an estimated $1,000 or more to the price of the system for each distinct camera location (multiple cameras can be at one location, as in exhibit 2.8). In many cases, however, wireless may be cheaper (and certainly easier) than running cabling.
Acceptable distances between a transmitter and receiver may range up to about 1,500 feet if the camera transmitter is in direct line-of-sight of the receiver. If equipment is located such that data transmissions must go through walls, fences, and so forth, the detail of the transmission can quickly degrade if the transmitter/receiver distance is already close to the manufacturer's recommended maximum distance. Installation distances to be implemented for camera transmissions should be much less than manufacturer recommendations if the transmitter and receiver are not within each other's line of sight.
The advantage of wireless camera systems is, of course, that cabling does not have to be run underground, through the air, or behind walls and ceilings. Therefore, the chance of tampering is much less. However, wireless applications where distances are close to manufacturer limitations may experience interference from very unusual sources, e.g., a nearby parked truck. Previous installation experience is usually required to set up such a system, due to the different antennas available that can perform differently in unique setups.
Short-distance, low-power RF transmission systems, such as a school's wireless camera system, usually do not require licensing by the Federal Communications Commission (FCC). Higher power systems will require an FCC license.
Research Report: The Appropriate and Effective Use of Security Technologies in U.S. Schools