For the most part, many systems still employ traditional FM broadcasts; others are trunked analog or digital systems. The incompatible OpenSky format is used by a small number of other police radio systems, the most notable of which being the Milwaukee Police Department and the Pennsylvania State Police.
Analog police radios use a dial to select frequencies, while digital radios use buttons for the same purpose. Most newer radios will accept either type of signal. An analog receiver can also be called a tuner or a radio. Older models were more limited, only receiving on a few designated channels.
Police officers use hand-held radios to communicate with each other and commanders. These devices can be portable or mounted on a vehicle. Portable units can be carried in vehicles to provide instant communication at any time. Stationary units often are mounted on a wall or placed on an officer's belt to provide coverage for large areas. Both types of radios can receive signals from multiple sources simultaneously.
All-digital police radios use a computer chip to convert the radio signal into data that computers can understand. This allows the radios to transmit and receive different types of signals simultaneously, such as voice transmissions one moment and data the next. Digital scanners can tune through all available channels at once, providing officers with instant updates on what's happening on each frequency.
Digital mobile radios have the ability to connect directly to computers using wired or wireless connections.
But some agencies have started to deploy digital technology into their radio networks. These digital systems can transmit more information faster than an FM signal, so they allow officers to communicate with each other and dispatch centers while keeping traffic alerts out over crowded frequencies.
Digital technology is found in a few different forms. There are primarily two types: narrowband and wideband. Narrowband systems use frequencies that are compatible with standard FM receivers; they can handle up to 20 channels. Wideband systems use frequencies that are higher in order to accommodate more users at one time. They can support 128 channels.
These systems have several advantages over conventional FM radios. First, by using digital technology, agencies can provide real-time updates on traffic incidents as they happen instead of having to wait until later when they get to their station. This can be very useful if an officer is working a hot spot and needs to notify colleagues about a current situation before moving on to another call. It also allows them to send prerecorded messages to all their officers via their mobile devices. Finally, computers can process much more information than humans can, such as knowing which channels need to be monitored in case someone calls for help.
Police Scanners on the Internet Because of the crisper sound and wider range of reception, larger cities are moving to digital networks. Digital police scanners, which are more costly than analog scanners, pick up analog, trunked, and digital radio signals. They can distinguish traffic alerts and other important information from other radio transmissions.
Analog scanners do have one advantage over their digital counterparts: they are less reliable. Because analog signals decay over distance, these scanners need to be placed in front of a window or opposite a door where they can catch passing vehicles. But this also means that they are vulnerable to interference from buildings, power lines, and other devices that produce electromagnetic waves.
Digital scanners work by converting radio frequencies into digital data that computers can understand. These signals can be recorded on computer tapes or disks for later review. They can also be transmitted real-time to officers in the field via the Internet or other wireless networks.
Analog scanners are less expensive to purchase but require more maintenance. The unit must be taken out of service when not in use to prevent damage due to heat buildup. Also, special filters need to be installed to remove noise from vehicle engines and other machinery that would otherwise interfere with signal reception.
Overall, a digital scanner has advantages over an analog one because it is less likely to miss important information due to signal degradation over distance.
Analog (non-digital) radio signals are picked up by traditional police scanners. Frequencies may be input and saved in the scanner's memory using a keypad. Analog radio broadcasts are used in many smaller towns and rural regions. Digital scanners can also receive analog transmissions but they do so automatically with the aid of special decoding software. Most larger cities use only digital scanners.
Analog scanners have two main advantages over their digital counterparts: cost and portability. An analog scanner is less expensive than its digital counterpart and this allows police departments to purchase more units for other areas of the city or county. Portable analog scanners are convenient because they can be taken anywhere there is a police activity happening. However, these scanners cannot transmit data digitally which limits their usefulness for large areas or remote locations without cell phone service.
Analog scanners were once the only option available to law enforcement agencies but today most large cities use only digital scanners. This change occurred due to improvements made by scanner manufacturers to the technology used in digital scanners. These advancements allow for higher quality scans of large areas quickly while using less power which reduces costs. In addition, digital scanners can be customized by radio dealers and scoped out by officers who then upload specific lists of stations to be scanned into the unit. This feature is not available on analog scanners.
However, the great majority of US law enforcement organizations continue to use radio channels compatible with the small $30 technical marvels. Amateur radio (HAM) operators can use the programmable portables on their two-meter and 70-centimeter frequencies, which are close to the public safety bands. These ports usually be found in fire stations, police departments, and other emergency response facilities.
A few large cities have municipal wireless networks that can be used by officers as a replacement for patrol radios. These tend to use long-range digital technology instead of radio waves, so they do not interfere with HAM radio traffic.
Some police agencies have adopted smartphone applications as an alternative to traditional radio systems. These can provide real-time updates on crime scenes and suspects, as well as dispatch commands. They are typically free apps that can be downloaded onto any mobile phone, but some require special hardware such as GPS receivers.
In conclusion, police use many different tools to communicate with one another and with citizens. From horse patrols to helicopter flybys, from foot beats to car chases, police work is never done. However, most of them rely on some form of communication technology to do their jobs.