Police radio is a radio system used by police and other law enforcement agencies to communicate with one another. Police radio systems almost always use two-way radio systems to allow for communications between police officers and dispatchers. Most modern police radio systems are encrypted, and many jurisdictions have made listening to police radio frequencies as a private citizen illegal. History Before police radio systems were first implemented, police officers assigned to their beat could only communicate with police command using telephone booths, call boxes, police boxes, or physical meetings. Calling for help or signaling other officers could only be done by shouting, using a whistle, or hitting things to make sounds. This meant that properly calling for assistance, reporting an incident or arrest, being dispatched to handle a crime, or requesting police resources was only possible if the officer reached a telephone or call box. The first police radio systems were implemented in Detroit in 1928, when the Detroit Police Department set up a one-way radio system to broadcast crime information to police cars. The frequency was assigned the call sign "KOP" by the Federal Communications Commission. To follow FCC regulations, KOP was described as an "entertainment station"; to fulfill this, KOP was made publicly accessible, and music was broadcast between descriptions of stolen vehicles and crime reports. The first two-way police radio system was implemented by the Bayonne, New Jersey police in 1933. The FCC briefly prohibited police radio communications in 1934, but rescinded their decision in 1935. Due to their cost and size, early police radio systems were only used in police cars and buildings; officers on foot patrol still had to rely on telephones and call boxes. Portable radios introduced in the 1960s made radio communications widely accessible to all officers. Early portable radios were heavy and had short battery life, an issue that gradually disappeared as technology advanced. Modern police radio systems are often augmented by mobile data terminals to effectively manage units and assignments. Police radio systems historically used public radio frequencies, and listening to them was, for the most part, legal. Most modern police radio systems switched to encrypted radio systems in the 1990s and 2000s to prevent eavesdroppers from listening in. By country Canada In Canada, the Radiocommunication Act states that it is illegal to intercept private radio communications with the intent to divulge or use any information obtained in the interception. This