06Police, fire and the radios that dispatch them

The short version: Police officers, firefighters, paramedics, railroads and utilities talk on land mobile radio, a push-to-talk system that runs alongside cell phones rather than through them. In the US, many large public safety systems use the digital P25 standard, and first responders also have a dedicated broadband network, FirstNet, on 700 MHz. Greater Boston adds a regional twist: its police mutual aid network, BAPERN, lives on T-Band channels that Congress once ordered sold off and then saved. The same airwaves carry warnings to the public, from the weather radio on 162 MHz to the alert that makes every phone in a room go off at once.

What is the radio on an officer's shoulder?

What you see: A handheld radio on a vest, a speaker-microphone clipped near the collar, and a bigger radio mounted in the cruiser or fire truck.

That is land mobile radio (LMR), the push-to-talk radio of police, fire, EMS, utilities, transit and railroads. CISA, the federal cybersecurity and infrastructure agency, describes a typical LMR system as handheld portables, mobile radios in vehicles, base stations, a network tying them together, and repeaters⁸².

A repeater is a radio at a high site that receives what a handheld sends and retransmits it. In CISA's words, "Repeaters are used to increase the effective communications range"⁸². Without a repeater, radios talk directly to each other on one frequency, usually called simplex. That works across a fire scene and fails across a city, because a handheld puts out little power from shoulder height.

US public safety LMR runs on VHF, UHF, 700 MHz and 800 MHz⁸². CISA warns that "Systems that operate on different frequencies are not always interoperable," so agencies use bridging devices to patch one system into another⁸². A town on VHF and a neighbor on 800 MHz cannot talk radio to radio without that kind of help.

There are two ways to organize the channels:

On a trunked system, users join a talkgroup, a virtual channel that the computer maps onto whichever real frequency is free for each conversation.

What is P25, and what does "Phase 2" mean?

What you see: A department announcing a new "digital radio system," or a scanner listing that says "P25 Phase 1" or "P25 Phase 2."

P25 (Project 25) is the North American standard for digital public safety radio. It was established in October 1989 by APCO, NASTD and three federal bodies: the NCS, NTIA and NSA⁸⁴. Its central promise is the Common Air Interface, which lets radios and infrastructure work together regardless of who made them; the Department of Homeland Security runs a Compliance Assessment Program to test that claim⁸⁴. Before standards like this, a department that bought one vendor's radios could find itself locked into that vendor.

P25 comes in two phases:

FDMA divides spectrum into separate frequencies; TDMA divides one frequency into separate turns in time. Phase 2 meets the FCC's 6.25 kHz-equivalent efficiency target in VHF, UHF and 700 MHz⁸⁴, which in practice means two conversations where Phase 1 fit one. The Phase 2 standard was approved in November 2010, and Motorola began shipping Phase 2 systems in August 2011⁸³.

On a trunked P25 system, a control channel assigns the voice channels. On a conventional P25 system, each packet carries a 12-bit Network Access Code (NAC) in place of the analog CTCSS and DCS tones older radios used to keep groups apart⁸³.

The standard also "supports secure communication through the use of encryption, key management, and equipment authentication"⁸⁴. Encryption is an option an agency turns on, not a default of P25, and that option is the technical root of the debate covered in scanners. For how a 911 call becomes a dispatch on these radios, see the sister guide at https://works.cold.fyi/911/.

What is FirstNet?

What you see: A rugged phone, tablet or vehicle modem used by a first responder, carrying data rather than push-to-talk voice over the traditional radio.

FirstNet is the US nationwide broadband network for first responders. Congress created it in Title VI of the Middle Class Tax Relief and Job Creation Act of 2012, signed February 22, 2012, as an independent authority within the NTIA at the Commerce Department⁸⁵. Congress provided $7 billion from spectrum auction revenues⁸⁵.

It runs on Band 14: 20 MHz of paired 700 MHz spectrum, 758-768 MHz from tower to device and 788-798 MHz from device to tower, which combined existing public safety broadband spectrum with the 10 MHz "D Block"⁸⁵.

On March 30, 2017, FirstNet awarded AT&T a 25-year contract, with $6.5 billion in FirstNet funding over the first five years; AT&T committed $40 billion over the life of the contract and access to infrastructure valued at more than $180 billion⁸⁵. By January 2018 all 50 states and 6 territories had opted in, though opting in does not oblige any agency to subscribe⁸⁵.

FirstNet is a separate system from the LMR radios above; a department can use both.

In its fiscal 2025 annual report, covering October 2024 to September 2025, the FirstNet Authority reported more than 7.8 million device connections and about 30,600 subscribed public safety agencies and organizations.⁸⁶ The initial nationwide buildout finished in March 2023, and in 2023 the FCC renewed the Band 14 license for ten years, contingent on the FirstNet Authority being reauthorized by February 22, 2027, the date it otherwise sunsets.⁸⁶ The same report says the House passed H.R. 7386 in April 2026 to extend the authority through September 2037, but that it was not yet law.⁸⁶

In Boston: what are BAPERN and the T-Band?

What you see: A scanner listing for Greater Boston with entries like "BAPERN 3," "BAPERN Central" or "MetroFire," on frequencies in the 470 MHz range.

BAPERN, the Boston Area Police Emergency Radio Network, has been developed and maintained by the Greater Boston Police Council since the early 1970s⁸⁷. It has more than 120 full member agencies, wide-area channels BAPERN 3 and 4, and district channels for the North, North-West, West, Central and South areas⁸⁷. It is a simulcast system - several transmitter sites sending the same signal at once - with voting receivers linked to Boston Police Headquarters, and each radio sends a unique ID that is logged with the voice traffic⁸⁷. A voting receiver setup listens at several sites and picks the clearest copy of each transmission.

Most of it runs on the T-Band, 470-512 MHz⁸⁸. According to CISA:

Boston and Cambridge police earlier used 460 MHz⁸⁹. The 6 MHz blocks are numbered like the UHF television channels they share space with.

CISA counts more than 200 T-Band licensees in Metro Boston, and a common regional channel plan covering more than 6,000 police, fire and EMS radios⁸⁹. A 2007 waiver yielded 32 repeater pairs and 6 simplex channels for that plan⁸⁹. MetroFire, a group of 34 communities, uses T-Band for fire mutual aid, and CISA cites the April 2013 Marathon bombing response as showing the strength of the region's shared radio⁸⁹.

The near-miss. Section 6103 of the same 2012 law that created FirstNet required public safety T-Band to be auctioned⁸⁸. For Greater Boston, that meant planning to move thousands of radios. The Don't Break Up the T-Band Act, part of the Consolidated Appropriations Act, 2021, signed December 27, 2020, repealed the auction mandate⁸⁸.

The newer layer. A 700 MHz P25 simulcast trunked overlay was in service when CISA wrote its case study, with seven sites and 10 to 12 planned⁸⁹. Boston Police itself moved to an encrypted digital system on August 9, 2025⁹⁰; scanners covers what that means for listeners.

What is that chatter near the train tracks?

What you see: Short calls between a train crew and a dispatcher or a track crew, heard on a scanner near a rail line, often in plain analog FM.

US railroads have their own block of VHF channels. NTIA's engineering report puts the railroad band at 160.215-161.565 MHz, with an existing plan of "181 frequencies, spaced every 7.5 kHz," while older analog equipment used 15 kHz channels⁹¹. As of NTIA's 1999 report, an industry-government Wireless Communications Task Force was planning a migration to narrowband digital radio⁹¹.

Much of that traffic is still analog. RadioReference's listings for Arkansas, as one example, show conventional analog FM channels between about 160.025 and 161.550 MHz for BNSF, CPKC, Union Pacific and shortline railroads⁹². The same listings note that railroads plan to move some secondary operations to the digital NXDN format, which not every scanner decodes⁹².

Utilities and transit agencies run their own LMR systems too.

What is the loud tone before an emergency message on TV or radio?

What you see: A harsh two-tone alarm and a crawl or voice announcement interrupting a broadcast, or a scheduled "this is a test."

That is the Emergency Alert System (EAS). Its lineage starts with CONELRAD, created under President Truman in 1951; the Emergency Broadcast System replaced it in 1963 under President Kennedy, and the FCC replaced that with EAS between 1994 and 1997⁹³. EAS participants include broadcasters, cable, wireless cable, satellite radio and, since May 2007, direct broadcast satellite TV⁹³.

Three agencies share the job. The FCC sets the technical rules, FEMA handles national activation and testing, and the National Weather Service issues weather alerts⁹³. FEMA's IPAWS system distributes digital alerts to broadcast, computers and phones⁹³. The first nationwide EAS test ran on November 9, 2011, at 2:00 p.m. Eastern, and lasted about 30 seconds⁹³.

Why did every phone in the room go off at once?

What you see: A loud tone and vibration on every phone nearby, with a short message about weather, a missing child or a local emergency.

That is a Wireless Emergency Alert (WEA), launched in April 2012⁹⁴. Alerts go out by cell broadcast: one message sent to every phone connected to the chosen cell towers, not a text to a list of numbers. That is why the phones of strangers sitting beside you go off at the same moment.

FCC rule changes since launch, per the FCC⁹⁴:

What is on 162.475 MHz?

What you see: A small "weather radio" on a kitchen counter or boat that stays silent until it blares an alarm, or a robotic voice reading forecasts on a scanner.

NOAA Weather Radio is the National Weather Service's own broadcast network. It runs 24 hours a day on seven VHF channels from 162.400 to 162.550 MHz, from 1,035 stations as of April 2025; each station covers about 40 miles (about 65 km), and together they reach more than 95% of the US population⁹⁵.

The trick that makes a weather radio useful at 3 a.m. is SAME (Specific Area Message Encoding): digital codes that activate only the receivers set for a given county or marine area⁹⁵. The NWS calls SAME the primary activator for EAS, so a weather warning on NOAA Weather Radio is often what triggers the tones on local TV and radio⁹⁵. A January 1975 White House policy named the network "the sole Government-operated radio system" for warnings into homes⁹⁵.

In Boston, the NOAA Weather Radio signal is on 162.475 MHz from Blue Hill, Massachusetts, according to the Town of Weymouth⁹⁶.

Elsewhere in the world

What you see: A national alert on a phone in Europe or the UK, sometimes with a different name and sound from the US version.

European Union. Article 110 of the European Electronic Communications Code requires member states to send "geo-targeted emergency alerts to all mobile phones located in the affected area," with a deadline of June 2022⁹⁷. EENA, the European emergency number association, reported that many countries missed it and still lacked compliant systems as of September 2023⁹⁷. France's FR-Alert combines cell broadcast with location-based SMS⁹⁷.

United Kingdom. The UK's Emergency Alerts system had its national test at 3 p.m. on Sunday, April 23, 2023, after pilots in East Suffolk and Reading⁹⁸. It works on 4G and 5G phones by mobile broadcast, reaches nearly 90% of phones in an area, and sounds and vibrates for up to 10 seconds⁹⁸.

UK emergency services radio. UK emergency services use Airwave, a TETRA (Terrestrial Trunked Radio) network.⁹⁹¹⁰⁰ Its planned replacement, the Emergency Services Network (ESN), is run by the Emergency Services Mobile Communications Programme and is meant to carry voice, video and data over a 4G/5G network; BT/EE holds the mobile services contract and IBM the user services contract, both in effect since December 2024.¹⁰⁰

The government's summary business case of July 27, 2026 puts the whole-life budget at £19.1 billion to 2043/44, with £6.1 billion already spent, and gives no Airwave shutdown date, saying only that it will close "when it is safe to do so."¹⁰⁰ Ofcom says the national Airwave infrastructure provision is planned to expire on December 31, 2026, and that ESN will serve England, Scotland and Wales.¹⁰¹

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