Glossary

Plain-language definitions of technical terms used throughout this guide.

A

Amateur radio— also: ham radio, amateur radio operator, ham
Amateur radio (also called ham radio) is a globally licensed radio service regulated by national telecommunications authorities in each country, operating under international agreements administered by the ITU. Licensed operators — called hams — can use a wide range of frequencies and power levels for personal communication, experimentation, and public service. Amateur radio operators provide a significant share of emergency communication support worldwide. Licensing requires a technical exam in most countries.Learn more →
AREDN
AREDN (Amateur Radio Emergency Data Network) is a project that repurposes off-the-shelf WiFi hardware (primarily Ubiquiti devices) to operate on amateur radio frequencies. The result is a high-bandwidth mesh network that can carry voice, video, and data — far more capacity than LoRa-based systems. Operating on amateur radio frequencies requires a license but allows higher power and more flexibility than unlicensed WiFi. AREDN networks are deployed by amateur radio clubs around the world specifically for emergency communication.Learn more →

C

CERT
CERT (Community Emergency Response Team) is a program that trains community members in basic disaster response skills: fire safety, light search and rescue, team organization, and disaster medical operations. CERT teams work alongside professional emergency services, not in place of them. The program originated in Los Angeles and is now active in many countries under different names. CERT teams are a natural home for neighborhood communication networks.Learn more →
Circumvention
Circumvention refers to tools and methods used to bypass internet filtering, censorship, or surveillance. This includes VPNs (Virtual Private Networks), the Tor network, and specialized tools like Psiphon and Lantern. Circumvention is distinct from offline communication — it assumes some internet connectivity exists but is censored, whereas mesh and radio techniques address scenarios where connectivity is absent entirely.

G

GMRS
GMRS (General Mobile Radio Service) is a radio service licensed by the US FCC for short-range personal and family communication. A single license covers an entire household and is valid for 10 years. No technical exam is required — only a fee and an application. GMRS radios are widely available and inexpensive. Outside the United States, equivalent services exist under different names and regulatory bodies — PMR446 in Europe, for example.Learn more →

I

Internet shutdown
Internet shutdowns are deliberate disruptions of internet or mobile data services, typically ordered by governments. They can be total blackouts (all connectivity cut) or partial (specific services like social media blocked). They are increasingly common during elections, protests, and conflicts. Local mesh networks, LoRa radio, satellite services, and circumvention tools can all provide communication paths that bypass or survive these shutdowns to varying degrees.Learn more →

L

LoRa— also: LoRa radio
LoRa (Long Range) is a radio modulation technique developed by Semtech. It trades data speed for range and power efficiency — a LoRa device can transmit several kilometers on a small battery, but can only send short, slow messages. This makes it well-suited for text messaging, position tracking, and sensor data in off-grid scenarios. Meshtastic uses LoRa as its underlying radio technology.Learn more →

M

Mesh network— also: mesh networking, mesh networks, mesh
In a mesh network, devices (called nodes) communicate directly with each other and forward messages on behalf of other nodes. If one node fails, traffic automatically routes around it. This makes mesh networks far more resilient than hub-and-spoke designs, where failure of the central hub brings the whole network down. Mesh networking is used in both WiFi systems (like AREDN) and long-range radio systems (like Meshtastic).Learn more →
Meshtastic
Meshtastic is open-source firmware that runs on small, low-cost LoRa radio modules. Devices running Meshtastic form an automatic mesh network — each device extends the range of the others by relaying messages. Users communicate via a smartphone app connected to the device over Bluetooth. The system requires no internet, no cellular network, and no central server. It is well-suited for neighborhood-scale text messaging and position sharing during emergencies.Learn more →

N

Net control
In amateur radio and emergency communication, a 'net' is a scheduled gathering of radio operators on a shared frequency. Net control is the station that runs the session — calling for check-ins, acknowledging stations, and managing traffic. Rotating net control among team members ensures more people are trained to run a net independently when needed.
Node— also: nodes
A node is the basic building block of any network. In a mesh network, each node both uses the network and helps extend it by relaying traffic for other nodes. In practice, a node might be a Meshtastic device clipped to a backpack, a WiFi router mounted on a rooftop, or a repeater on a hilltop.

P

Power resilience
Power resilience means ensuring your communication equipment has a power source that survives the same events that cut communications — storms that knock out the grid, earthquakes that destroy substations, or intentional shutdowns. Common approaches include battery banks (hours to days of runtime), solar panels with charge controllers (indefinite runtime in sufficient sun), and generators (requires fuel). The most resilient systems use multiple power sources and know the power budget of each device.
PSK— also: pre-shared key
A Pre-Shared Key (PSK) is a secret value that is distributed to authorized devices or users before communication begins. In Meshtastic, setting a PSK on a channel means only devices that know the key can read the messages — others can hear the radio signals but cannot decode them. PSKs must be distributed securely (in person, not over the network being secured) before an emergency.

R

Repeater— also: repeaters
A repeater listens on one frequency and simultaneously re-transmits what it hears on another. Because repeaters are usually located at elevation (hilltops, tall buildings, towers), they can serve a much wider area than a handheld radio can reach on its own. Many amateur radio clubs maintain repeaters that remain operational during disasters. A repeater is a single point of failure — if it goes offline, everyone relying on it loses coverage.Learn more →

S

Simplex
Simplex means two radios communicate directly, on the same frequency, without going through a repeater or any intermediate infrastructure. Range is limited by the power and antenna of the radios involved and the terrain between them, but simplex is the most resilient mode — it works even when all repeaters and infrastructure are offline. Most playbooks recommend a designated simplex frequency as a fallback when other communication paths fail.
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