13The radios you carry without knowing

The short version: Plenty of transmitters in your life have no screen and no Wi-Fi icon. The electric meter on your house radios its readings to the utility, each tire on a modern car reports its own pressure, the card or phone you tap at a subway gate talks to the reader over a few centimeters of air, and a toll tag answers every gantry you drive under. In Massachusetts, both big electric utilities are swapping in radio-equipped meters through 2027, and since August 2024 the MBTA has taken a bank card or phone directly at the gate.

What is that new electric meter, and does it transmit?

What you see: A meter with a digital display and no spinning dial, sometimes with a sticker or door hanger saying it was upgraded.

These are AMI meters, short for advanced metering infrastructure: meters that report usage over a two-way network instead of waiting for someone to walk by and read them. A common US design is a radio mesh in the 902-928 MHz band (one of the unlicensed ISM bands). In Itron's OpenWay system, documented in a white paper published by the Canadian utility BC Hydro, each meter sends its own data one to three times a day and also relays its neighbors' data, hopping toward routers mounted on utility poles that carry it back to the utility.²²⁹ Transmit power is "one watt or less."²²⁹

The meters are quiet most of the time. Across 12,969 BC Hydro meters, the average time spent transmitting was 2.99 minutes per day, a duty cycle (the fraction of time a transmitter is actually sending) of 0.21%.²²⁹ Those figures describe BC Hydro's network; other utilities and meter generations may differ.

Some people object to having a transmitter on their home, on health or privacy grounds, and utilities offer opt-outs in some places (see below). This section takes no side; what health agencies and researchers say about RF exposure is in health.

When is Eversource installing smart meters in Massachusetts?

What you see: A letter or text from Eversource scheduling a meter swap.

Eversource is replacing its Massachusetts meters with Itron Gen 5 meters, installed by the contractor Grid One Solutions, in a project expected to take about three years.²³⁰ Installs began in July 2025 in Springfield, with about 1.5 million meters to upgrade.²³¹ By October 31, 2025, more than 35,000 meters had gone in across western Massachusetts; eastern Massachusetts was to follow in early 2026 after network upgrades, with a target of up to 60,000 meters a month by spring 2026.²³¹

On January 13, 2026, Eversource reported 100,000 meters installed out of more than 1.5 million planned, said the communications devices in eastern Massachusetts were "more than 75 percent complete," and repeated a finish date of late 2027.²³² Eversource also cites a figure that more than 76% of US meters are already smart.²³¹

Eversource has said little in public about the radio itself. A May 15, 2025 Eversource notice posted by the Town of Chilmark says the meter "doesn't rely on Wi-Fi" but on "a safe and secure Eversource network,"²³³ and Eversource's smart meter safety page, which does not say which service area it covers, lists the meter's frequency as "902 -2000 MHz."²³⁴

The same notice set the eastern Massachusetts schedule: network equipment between August 2025 and the end of July 2026, and meter replacement "between March 2026 and the end of 2027."²³³

Can I opt out of a National Grid smart meter in Massachusetts?

What you see: A National Grid notice in the mail, or a town website post about upcoming meter work.

National Grid is running the same kind of program. As of April 23, 2026, it had installed more than 500,000 smart meters in Massachusetts, over 35% of its target, and plans to reach all 1.4 million electric customers by the end of 2027.²³⁵ One feature it highlights: the new meters signal the control room when they lose power, so the utility can see an outage without waiting for phone calls.²³⁵

There is an opt-out. According to a notice posted by the Town of Salisbury ahead of a May 21, 2026 resource fair, residential customers on National Grid's R-1 and R-2 rates can ask for a non-communicating meter that is read by hand, for a fee, at ngrid.com/optout.²³⁶ The notice does not state the fee amount.²³⁶

Eversource offers an opt-out as well. In May 2025 it said residential customers who keep a manually read meter pay $34 a month, plus a one-time $42 service fee,²³⁷ and in October 2025 it said it would waive the $42 fee for customers who opt out within the 90-day notice period before installation.²³⁸

What frequency do tire pressure sensors use?

What you see: An amber dashboard light shaped like a horseshoe with an exclamation point, usually on the first cold morning of fall.

Each wheel on a modern car holds a small battery-powered transmitter that reports that tire's pressure. This is the tire pressure monitoring system (TPMS). In the US, Federal Motor Vehicle Safety Standard 138, adopted under the TREAD Act, requires TPMS on passenger vehicles, trucks and buses from the 2008 model year, meaning those built after August 31, 2007.²³⁹ The system must warn the driver when a tire is 25% or more below the pressure on the door-jamb placard.²³⁹

The sensors send short frequency-shift-keyed bursts, about 7.5 milliseconds each, at 315 MHz or 434 MHz; 434 MHz is the European choice.²⁴⁰ One widely used sensor chip from Freescale supports both frequencies.²³⁹ The European frequency sits in the 433.05-434.79 MHz ISM band, which exists only in ITU Region 1 (Europe, Africa and the Middle East).²⁰²

Air in a tire loses pressure as it cools, which is why the light tends to come on with the first frost.

Car key fobs send similar short bursts. According to an Analog Devices overview, remote keyless entry systems in the US and Japan most commonly use 315 MHz, and in Europe 433.92 MHz, with Europe also opening 868 MHz.²⁴¹ In the US, fobs, garage door openers and similar remotes fall under 47 CFR 15.231, which covers periodic transmitters at 40.66-40.70 MHz and above 70 MHz sending control signals "such as those used with alarm systems, door openers, and remote switches." Continuous transmissions, voice, video and radio control of toys are not permitted, and a manually operated transmitter must shut off within 5 seconds of being released.²⁴²

How does tap-to-pay work, and how close do I need to be?

What you see: The four curved lines of the contactless symbol on a card, phone screen or fare reader.

Transit cards, tap-to-pay bank cards and phone wallets use NFC (near-field communication) or closely related contactless-card standards, usually at 13.56 MHz.²⁴³ That frequency sits in a worldwide ISM band, 13.553-13.567 MHz.²⁰²

The card has no battery. The reader creates a magnetic field, and the card's coiled antenna picks up enough energy by induction to power its chip and answer.²⁴³ That is why range is so short. "Proximity" cards built to the ISO 14443 standard work up to about 10 cm (4 inches), while "vicinity" cards under ISO 15693, used more for tags and access badges, can reach more than 1 m (3 feet).²⁴³ The short range is a feature: you have to bring the card to the reader on purpose.

This is one kind of RFID (radio-frequency identification). RFID tags can be passive, powered by the reader like a tap card, or active, with their own battery, like a toll tag.

Is the CharlieCard being replaced?

What you see: The green CharlieCard, or a fare gate at an MBTA station with a reader that accepts phones and bank cards.

The CharlieCard went into service on December 4, 2006, replacing the token on the MBTA.²⁴⁴ It uses NXP's MIFARE Classic chip.²⁴⁴ In March 2008, Karsten Nohl's team reported that MIFARE Classic's security was broken.²⁴⁴ That August, the MBTA sued a group of MIT students (MBTA v. Anderson) over a DEF CON 16 talk; on August 19, 2008, the court allowed the talk to go ahead.²⁴⁴

The replacement is arriving in stages under the MBTA's fare program known as AFC 2.0. The MBTA board approved a $723 million contract with Cubic in November 2017, revised to more than $900 million in December 2019.²⁴⁴ Contactless bank cards and phone wallets started working at the gates on August 1, 2024.²⁴⁴ By January 2025, the Boston Globe reported, "tap to ride" had passed 10 million taps and covered every bus, every Green Line and Mattapan trolley, and every gated subway station; contactless payments rose from 7% of fares in the first month to 16% by December 2024.²⁴⁵ Public testing of a new CharlieCard began in December 2025.²⁴⁴

So the answer is yes, gradually: a new CharlieCard is in testing, and you can already skip the card and tap a bank card or phone.

As of October 7, 2026, MacRumors reported that the MBTA was testing a new CharlieCard that also works in Apple Wallet on iPhone and Apple Watch, with testing limited to riders who signed up in 2024 and a public release due "at a later date."²⁴⁶

More on how the MBTA's fare system and stations work is in How a City Works.

How does E-ZPass work?

What you see: A gray plastic box behind your rearview mirror, and steel gantries over the highway with no toll booths underneath.

E-ZPass tags are active RFID transponders: they carry their own battery, unlike a tap card. They work at 915 MHz, in the 902-928 MHz band available only in the Americas, using a time-division protocol at 500 kbit/s, and have historically been made by Kapsch (formerly Mark IV).²⁴⁷²⁰² In plain terms, the gantry reads the tag's ID as the car passes underneath, and the toll is charged to the account linked to that tag.

E-ZPass was first deployed on the New York State Thruway, at the Spring Valley toll plaza, on August 3, 1993, and by December 1996 it covered all of the Thruway's fixed-toll barriers.²⁴⁷ As of 2024 the network covered 20 states, including Massachusetts, where the older Fast Lane system was rebranded E-ZPass in 2012.²⁴⁷

How do highway signs know the travel time?

What you see: An overhead message board reading something like "BRAINTREE 14 MIN."

In Massachusetts, many of those numbers have come from radios in passing cars. MassDOT first installed its travel-time system, which relies on roadside Bluetooth readers, in summer 2012.²⁴⁸ Each reader logs the MAC address, a hardware ID that a Bluetooth radio broadcasts, of devices going by, along with the time and place. When the same address shows up at two readers, the gap between them is a travel time, and a server takes the median of many such pairs.²⁴⁹ The system wants at least 3 signals in 15 minutes and 36 matched pairs an hour to post a reliable figure.²⁴⁹ By July 2013 it covered the route from Boston to Cape Cod, using TrafficCast's BlueTOAD readers.²⁴⁹

A 2014 expansion plan called for 132 travel-time signs fed by 121 Bluetooth readers, reaching all state highways by the end of that year.²⁴⁸

A reader logs a hardware address, not a name or phone number. Whether that makes the data anonymous is a question on which transportation agencies and privacy advocates can disagree. Turning Bluetooth off on your phone and car keeps them from being counted.

In Boston

• Meters: Eversource and National Grid both serve Massachusetts and both aim to finish by the end of 2027; Eversource said its eastern Massachusetts installs would start in early 2026.²³²²³⁵
• Transit: CharlieCard since 2006, tap-to-ride with bank cards and phones since August 1, 2024, and a new CharlieCard in testing since December 2025.²⁴⁴
• Roads: E-ZPass replaced the Fast Lane name in 2012,²⁴⁷ and MassDOT's Bluetooth readers have fed highway travel-time signs since 2012.²⁴⁸

For the city's other transmitters, from TV towers to harbor radio, see Boston.

Elsewhere in the world

• Tire sensors: Europe uses 434 MHz, in an ISM band that exists only in ITU Region 1; North America mainly uses 315 MHz.²⁴⁰²⁰²
• Toll tags and meters: The 902-928 MHz band used by E-ZPass and US meter meshes is an ISM band only in the Americas, so the same hardware does not carry over to Europe.²⁰²
• Bluetooth travel times: ENR reports that New Jersey's DOT uses the same technique, fused with E-ZPass reads, as does Philadelphia.²⁴⁹
• Tap cards: 13.56 MHz is a worldwide ISM band, so contactless cards and phones use the same frequency in London, Tokyo and Boston.²⁰²

Report an error in this section