A Brief History of Emergency Service Radio

Police, Fire Department and Ambulance are the three emergency services that nowadays use an integrated communication system. In this brief history you will find that the Police was often the first service to introduce new communication technology to the emergency services. The crime fighters always had the urge to keep up with the criminals and criminals are always apt to use the latest technology to their (detrimental) benefit.

Remember that the city police system as we know it now was first organized in Philadelphia in 1751. In New York, the city police was organized only in 1845. Up to the creation of city police, marshals and sheriffs enforced the law.

Wikipedia – Police

First Technology

The first technology used to communicate between police officers was the ratchet. Victorian, English police used the ratchet to call for help from any policeman in the area. In 1883 the police whistle was invented for a competition held by the London Metropolitan Police. The whistle was used to attract attention of the public and also attracted attention of other policemen. The ratchet and the whistle could only be used to attract attention, nothing else.

South Wales Police Museum &ndahs; PC James James
WikiPedia – James Hudson (inventor)
City of Irvine – The History of Police Communication


The telegraph allowed communicating from the patrolling police officer to the police station. The telegraph keys were placed into ‘Call Boxes’. The boxes were first developed as fire alarm boxes in 1852. The box contained a telegraph that could send a location code to the nearest fire station. The message was sent by breaking a seal and then pulling a lever. The police started to use similar boxes in 1870. The police box allowed reporting different crimes by turning a dial to point a specific crime and then pull the lever.

Gamewell-FCI – History
City of Irvine – The History of Police Communication


The telephone allowed two way communications, but they were not yet mobile. Telephones were placed in boxes similar to the fire alarm call boxes from around the 1880s. The ‘Police Box’ or ‘Private Box’ however also featured a red light on top. If a police officer on patrol saw the red light blinking, he knew he had to call the station for an assignment. The fire alarm call boxes did not contain a telephone. For communication back to the fire station, the fire fighters carried a hand held telephone that they could plug-in in the nearest fire alarm call box.

St.Louis Police Department – History

One-way Radio

With cars, the need for mobile communications rolled in. In the 1928 Detroit police cars were the first police cars to be equipped with radio. First the radio was only one way communication, allowing to “Calling all cars.” The radio dramatically improved response times. Messages were sent over AM radio frequencies. To report to the police station, the officer still had to go to a police box.  Although the fire department used radio sometimes, the fire department mostly relied on its fire alarm boxes.

LAPD – history 1926 – 1950
Unofficial History of the LAPD Communications Division
IEEE Milestones – One-way Police Radio Communication

Two-way Radio

Within five years of the first radio in 1933, two-way radio was introduced into the cars of the Bayonne, NJ police. The two-way radio was quickly adopted throughout the country. As communication was now possible between the police station and the cars, the police box quickly vanished. However, the old police box phones can still be seen in San Fransisco. In 1940 FM radio communication was introduced in Hartford, CT. The quality of the communication system was improved by using FM instead of AM.

IEEE Milestones – Two-Way Police Radio Communication
IEEE Milestones – FM Police Radio Communication
Virtual Museum of the City of San Francisco – Mayor’s Emergency Telephone System


With a car installed radio, the officer cannot communicate to the station when out of the car. To improve mobility, handheld radio communication devices were developed. At first they were big and expensive, used by the military in the Second World War. Galvin Manufacturing Corporation (later Motorola) created the Handie-Talkie. The first equipment to be called Walkie-Talkie was a 15kg back pack unit. It took until 1962 before Motorola introduced the 33-ounce “brick” walkie-talkie. The walkie-talkie is known for its Push To Talk (PTT) button.

IEEE Milestones – Evolution of the cellphone
Motorola – Timeline
Wikipedia – Walkie-Talkie

Trunked Radio System

An AM or FM two-way radio system uses one frequency to communicate. While in the beginning of radio communication one radio antenna was enough to cover a large part of Los Angeles, soon there was no space and time enough to transmit all messages for all districts and all emergency services. A growing number of frequencies were needed to service all districts and all emergency services. However, during quiet times all those frequencies were occupied without any use.

Early two-way radio systems communicated only on one channel. It required for every unit to listen in on one channel to hear reports. A unit or a group of units switched to another channel if a talkgroup (a group of users that belong for example to the same district and the same emergency service, other kinds of talkgroups are possible) conversation was needed. The switching was manual and the radio signal was analogue.

Trunked Radio System is a complex computer controlled radio system. The computer does the switches the communication for the various talkgroups. The system allows to use a limited number of frequencies for a maximum number of talkgroups. To further reduce the number of used radio frequencies, a digital signal is used now.

Wikipedia – Trunked Radio System


ARMER is the Minnesota state wide emergency radio system. The acronym stands for Allied Radio Matrix for Emergency Radio. ARMER is a fully digital, trunked radio system used for mobile, two-way communication between the command center and officers, fire fighters and other emergency personnel. The ARMER system was first introduced in the Twin Cities metropolitan area.

Currently (in 2011) the system is being rolled out to other areas in the state. For this purpose the state is divided in regions, each region having an organization that is responsible for rolling out the ARMER system in that region. The Central Minnesota Radio Board is responsible for rolling out ARMER in the counties that together form the central Minnesota region.

MN DOT – MN DOT as Owner of ARMER 
MN DPS – Emergency Communication Network