This glossary defines two-way radio and push-to-talk terms in one or two sentences each. A term with a page of its own links to it, and the rest are defined here with a source. Radio codes such as 10-4 and the spelling alphabet are in the radio codes tool, and the parts of a business radio system are in two-way radio systems for business.
What do the basic push-to-talk and two-way radio terms mean?
Two-way radio is the broad term for a radio that sends and receives, usually by push-to-talk. A walkie-talkie is a handheld one, land mobile radio is the professional class, and PoC sends the same calls over a mobile network. The rest of the glossary builds on these terms.
| Term | Meaning |
|---|---|
| Carrier PTT, also Operator push to talk, Verizon PTT+, AT&T EPTT | A push-to-talk service sold by a mobile operator and run on its own network. AT&T's Enhanced Push-to-Talk starts at $5 per user a month, October 2026.1 |
| Land mobile radio, also LMR, PMR (professional mobile radio) | Two-way radio between base stations and mobile or portable radios on land, run on private networks by public safety, utilities, transport and industry. The FCC defines the service as a mobile service between base stations and land mobile stations, or between land mobile stations.2 |
| Nextel, also iDEN, Direct Connect | An early cellular push-to-talk service. Direct Connect ran on Nextel's own iDEN network, which Sprint switched off on June 30, 2013.34 |
| OMA PoC, also Open Mobile Alliance PoC | The first open standard for PoC, from the Open Mobile Alliance. Version 1.0 was approved on June 9, 2006.5 |
| PoC, also Push-to-talk over cellular, PTToC, PoC radio | Push-to-talk over cellular: push-to-talk voice sent as data over a mobile network to a server, instead of over a radio channel of its own. The Open Mobile Alliance published the first open PoC standard in 2006.5 |
| PTT, also Push to talk, Press to talk | Push to talk: the speaker holds a key while talking and releases it to listen. Everyone in the group hears the call and only one person talks at a time.6 |
| PTT phone, also Push-to-talk phone, Rugged phone | A phone with a dedicated or programmable key that starts a push-to-talk service, so it works like a walkie-talkie over the mobile network. |
| Two-way radio, also Two way radio, Radio transceiver | A radio that both sends and receives voice, so people on one channel can talk to each other. Most work by push-to-talk, one speaker at a time. |
| Walkie-talkie, also Walkie talkie, Handheld radio | A handheld two-way radio. You press a button to talk and release it to listen, because everyone on a channel shares it. |
What do the digital radio standards mean?
A digital radio standard fixes how speech becomes data on a channel. DMR and P25 Phase 2 share one channel between two calls in time slots, dPMR and NXDN fit one call into 6.25 kHz, and TETRA puts four slots in 25 kHz. MCPTT is the matching standard for push-to-talk over LTE.789
| Term | Meaning |
|---|---|
| DMR, also Digital Mobile Radio | Digital Mobile Radio: an ETSI standard that splits a 12.5 kHz channel into two time slots, so one channel carries two calls.8 |
| dPMR, also Digital PMR | Digital PMR: an ETSI-based digital standard that fits one call into a 6.25 kHz channel.7 |
| MCPTT, also Mission critical push to talk | Mission-critical push-to-talk: the 3GPP standard for push-to-talk over LTE and 5G, completed in Release 13 in March 2016.10 |
| NXDN, also IDAS, NEXEDGE | A digital standard from Icom and JVC Kenwood, sold as IDAS and NEXEDGE, with one call per 6.25 kHz channel.7 |
| P25, also Project 25, APCO-25 | Project 25: a suite of TIA-102 standards for interoperable digital land mobile radio, built for public safety. Phase 2 uses two time slots and runs on trunked systems only.11 |
| TDMA, also Time-division multiple access, Time slots | Time-division multiple access: users share one channel by taking turns in time slots. DMR uses two slots per 12.5 kHz channel.128 |
| TETRA, also Terrestrial Trunked Radio | Terrestrial Trunked Radio: an ETSI standard for digital trunked radio, used by emergency services, transport and utilities. Each 25 kHz carrier holds four channels.9 |
What do frequency and signal terms mean?
These terms describe how a radio signal is placed and shaped. VHF and UHF are the two bands most two-way radios use, narrowband means a channel of 12.5 kHz or less, and frequency response and codecs describe how voice is carried through the radio.
| Term | Meaning |
|---|---|
| Analog radio, also Analogue radio, FM radio | A radio that sends voice by frequency modulation (FM), one call per channel. How it differs from digital is in analog vs digital radio. |
| Codec, also Voice codec, Opus, AMR | Coder-decoder: the part that turns voice into digital data and back. Digital radios and PoC apps each use one.13 |
| Frequency response, also Audio response | How a radio's audio level changes with pitch. For voice transmitters the FCC requires the maker to measure the audio modulating circuit from 100 to 5,000 Hz and report it as a graph or comparable data.14 |
| Narrowband, also Narrow band, 12.5 kHz channel | A channel of 12.5 kHz or less. Under FCC Part 90, stations must operate on channels of 12.5 kHz or less since January 1, 2013, unless they meet the efficiency standard.15 |
| UHF, also Ultra high frequency | Ultra high frequency: 300 MHz to 3 GHz.16 Motorola says UHF suits buildings and towns better than VHF.17 |
| VHF, also Very high frequency | Very high frequency: 30 to 300 MHz.16 Motorola says VHF travels farther in open outdoor areas.17 |
What do channel, squelch and tone terms mean?
A channel is the frequency radios share. Squelch mutes the speaker until a signal arrives, CTCSS and DCS tones make it open only for your group, and VOX starts sending when you speak. Simplex and duplex describe how the two directions share a channel. FRS, GMRS and PMR446 are the consumer services.
| Term | Meaning |
|---|---|
| Channel | The frequency, or pair of frequencies, a group of radios shares. PMR446 has 16 analog channels spaced 12.5 kHz apart.18 |
| CTCSS, also Sub-tone, Privacy code, PL tone | Continuous Tone-Coded Squelch System: the transmitter sends a continuous low tone and the receiver opens only when it hears the matching tone. The ETSI table lists 39 tones from 67.0 to 250.3 Hz.19 |
| DCS, also Digital-coded squelch, DCSS, DTCS | Digital-coded squelch: a 23-bit code sent continuously at 134.4 bit/s that opens a receiver set to the same code. ETSI lists 83 allowable codewords.19 |
| FRS, also Family Radio Service | Family Radio Service: a US radio service that needs no license, on 22 channels near 462 and 467 MHz, with a built-in antenna and up to 2 W effective radiated power.20 |
| Full duplex, also Duplex | Voice travels both ways at once, as on a phone call. 3GPP allows full-duplex private calls without floor control in mission-critical push-to-talk.21 |
| GMRS, also General Mobile Radio Service | General Mobile Radio Service: a US service on 462 and 467 MHz that needs an FCC license, $35 for ten years, and allows repeaters.22 |
| Half duplex | Voice travels in one direction at a time: hold the key to talk, release it to listen. Push-to-talk works this way.5 |
| PMR446, also PMR 446, License-free radio (EU, UK) | A license-free walkie-talkie service in Europe on 446.0–446.2 MHz, limited to 0.5 W effective radiated power with an integral antenna and no repeaters.18 |
| Simplex, also Direct mode | Radios talk to each other directly on a channel and take turns, with no repeater. The ATIS glossary notes that radio and telephony use the word in opposite senses.23 |
| Squelch | A circuit function that suppresses the audio output of a receiver, so the speaker stays quiet until a signal arrives.24 Tone squelch (CTCSS, DCS) also requires the right tone.19 |
| VOX, also Voice-operated transmit, Voice-operated exchange | The radio starts transmitting when it hears your voice, so no key press is needed. Sensitivity must match the room: Motorola's Talkabout T802 offers three levels, from high for quiet places to low for noisy ones.25 |
What do repeater, trunking and talkgroup terms mean?
System terms describe how radios are joined. A repeater extends range, trunking shares a pool of channels, a talkgroup is a named group of users, a dispatch console lets an operator manage them and RoIP carries a radio channel over IP. The business radio systems guide shows how they fit together.
| Term | Meaning |
|---|---|
| Dispatch console, also Dispatcher, Dispatch software | A PC application that lets an operator call radio groups, send text and see locations. One maker's console connects over IP to a radio server and covers conventional, IP Site Connect, Capacity Plus and Capacity Max systems.26 |
| Floor control, also Talk permission, Busy tone | The rule that decides who may talk at a given moment: it grants one request and rejects or queues the other. 3GPP defines it as arbitration for who may transmit.21 |
| Mouth-to-ear latency, also PTT delay, Voice delay | The delay from speaking into one device to the sound reaching the listener. 3GPP's MCPTT target is under 300 ms for 95 percent of voice bursts.21 |
| Repeater | A fixed transmitter that retransmits the signals of other stations, so a radio only has to reach the repeater, not the other radio.27 |
| RoIP, also Radio over IP, Radio gateway, Interoperability gateway | Radio over IP: a gateway carries a radio channel's audio and push-to-talk signal across an IP network, so radios, consoles and PoC services can join it.28 |
| Talkgroup, also Group, Channel group | A named group of users whose radios or apps hear each other. A call to the group reaches every member who has it selected; group calls are part of the DMR standard and of MCPTT.810 |
| Trunking, also Trunked radio system | A system that searches two or more paths and automatically assigns an open one to each call, instead of giving each group a fixed channel.2 |
What do PoC and mobile network terms mean?
A PoC radio runs on a mobile operator's network, so network terms decide whether it works: the LTE bands it supports, a SIM that allows data, roaming charges and signal strength. CDMA is an older access method that some operators retired.
| Term | Meaning |
|---|---|
| B20, also LTE band 20, 800 MHz | LTE band 20 (800 MHz): radios transmit on 832–862 MHz and receive on 791–821 MHz.29 |
| B28, also LTE band 28, 700 MHz | LTE band 28 (700 MHz): radios transmit on 703–748 MHz and receive on 758–803 MHz.29 |
| CDMA, also Code-division multiple access, 3G CDMA | Code-division multiple access: several signals share one wideband channel, each identified by its own code.30 Verizon scheduled the retirement of its 3G CDMA network for December 31, 2022.31 |
| eSIM, also Embedded SIM | An embedded SIM: a chip in the device that is provisioned remotely instead of by inserting a card. GSMA specifies remote SIM provisioning for any mobile device.32 |
| IoT SIM, also M2M SIM, Data-only SIM | A SIM sold for machine-to-machine devices, usually data only and used through the operator's APN. A data-only SIM is enough for an app-based PoC radio.3334 |
| LTE band, also Frequency band, Band number | A numbered block of radio frequencies defined for LTE. A PoC radio works on an operator's network only if it supports one of the bands that operator runs.29 |
| LTE network, also Long Term Evolution, 4G network | A mobile network built on LTE, Long Term Evolution, the 3GPP system enabled by E-UTRA and the Evolved Packet Core, often called 4G. PoC radios use it for voice and data.35 |
| Roaming, also EU roaming, Roam like at home | Using a mobile network outside your home country. In the EU and the EEA, calls, texts and data in another covered country are charged at domestic rates, subject to fair use.36 |
| RSRP, also Reference signal received power, Signal strength | Reference signal received power: the power of the LTE cell's reference signal at the device, in dBm. Values closer to zero mean a stronger signal.37 |
| VoLTE, also Voice over LTE, 4G calling | Voice over LTE: voice calls carried over the 4G LTE network instead of the traditional voice network.38 |
What do device rating, safety and location terms mean?
These terms say how a radio is built and what it reports: sealing and shock ratings, explosion-protection approval, the duty cycle behind battery claims, alarms for people who work alone, a remote talk button and location. Check the rating behind a marketing word before you buy for a harsh site.
| Term | Meaning |
|---|---|
| ATEX, also Intrinsically safe, Ex radio | The EU framework for equipment used in potentially explosive atmospheres (Directive 2014/34/EU). A radio for such a site carries an ATEX approval.39 |
| Bluetooth PTT button, also Remote PTT, BLE PTT | A button or headset key that connects to a phone by Bluetooth and starts transmission, so the phone can stay in a pocket. Apple's push-to-talk framework accepts Bluetooth accessory buttons.40 |
| Duty cycle, also 5/5/90, Talk-listen-standby | The mix of transmit, receive and standby time a maker uses to rate battery life. The common 5-5-90 cycle is 5 percent transmitting, 5 percent receiving and 90 percent standby.41 |
| Geofencing | A virtual boundary around a place, defined by a latitude, longitude and radius. Dispatch software can alert when a device enters or leaves it.42 |
| GNSS, also GPS, GLONASS, Galileo, BeiDou | Global navigation satellite system: any satellite constellation that provides worldwide positioning, navigation and timing. Galileo (EU), GPS (US), GLONASS (Russia) and BeiDou (China) are the systems in service.43 |
| IP rating, also IP54, IP67, Ingress protection | An IEC 60529 code: IP, then one digit for dust and solid objects and one for water. An X means that part was not tested.44 |
| Lone worker, also Man down, Fall detection | Someone who works without close or direct supervision.45 Radios can add a man-down alarm that sends an alert when the device detects a significant tilt, or when it has not moved within a preset time.46 |
| MIL-STD-810, also Military standard, Drop test | A US Department of Defense standard for environmental engineering considerations and laboratory tests. The current edition is MIL-STD-810H, dated January 31, 2019.47 |
| SOS button, also Emergency button, Panic button | A dedicated key that sends an emergency alert. Motorola's TLK 110 has a dedicated emergency button next to its lone worker and man-down features.48 |
What do radio codes and lingo mean?
Radio lingo is the short words and codes that keep calls brief: prowords such as over and out, Q-codes, 10-codes and the spelling alphabet. Meanings change between services and agencies, so the radio codes tool lists them with their source.
| Term | Meaning |
|---|---|
| NATO phonetic alphabet, also Spelling alphabet, Alfa Bravo Charlie | The 26 code words used to spell letters over the radio, from Alfa to Zulu. ICAO, ITU, NATO and IMO use the same words.49 |
| Proword, also Procedure word, Over, Out, Roger | A word with a fixed meaning in radio procedure. Over means the transmission has ended and a response is necessary; out means no answer is required or expected.50 |
| Radio codes and lingo, also 10-codes, Radio lingo, Radio jargon, Walkie-talkie codes | Short words and numbers that keep calls brief, such as prowords, Q-codes and 10-codes. FEMA's NIMS requires plain language rather than codes in multi-agency events such as major disasters.51 |
What do ham and hobby radio terms mean?
Hobby radio has its own vocabulary. Amateur radio is the licensed service for experimenters, a call sign names each station, Morse code is the oldest mode, CB is a license-free band on 27 MHz and a software-defined radio does its signal processing on a computer.
| Term | Meaning |
|---|---|
| Amateur radio, also Ham radio, Ham | A licensed, non-commercial radio service. The FCC defines it as a radiocommunication service for self-training, intercommunication and technical investigations by authorized persons with a personal aim and without pecuniary interest.52 |
| Call sign, also Callsign | The unique name of a licensed ham station, such as W1AW. The prefix shows the country and the national regulator issues it with the license. |
| CB radio, also Citizens Band | Citizens Band: a license-free two-way radio service on 27 MHz.53 |
| Morse code, also CW | Letters and numbers sent as short and long signals, dots and dashes, by sound, light or radio. A dash equals three dots.54 |
| SDR, also Software-defined radio | Software-defined radio: a radio system that performs the required signal processing in software, so one piece of hardware can be reprogrammed for many radio types.55 |
Questions
What does PTT stand for?
Push to talk. The speaker holds a key while talking and releases it to listen, and everyone in the group hears the call.6 More in what is push-to-talk.
What is the difference between PoC and LMR?
Land mobile radio runs on radio channels you license and build. PoC sends voice as data over a mobile operator's network. The full comparison is in LMR vs PoC.
What is the difference between UHF and VHF?
VHF covers 30–300 MHz and UHF 300 MHz–3 GHz.16 The practical difference is in UHF vs VHF.
Sources
- Enhanced Push-to-Talk · AT&T Business
- 47 CFR 90.7: Definitions, Private Land Mobile Radio Services · Cornell LII, US Code of Federal Regulations
- Nextel, Motorola celebrate 10 years of Direct Connect (2002) · RCR Wireless News
- Sprint's iDEN Nextel Shuts Down and Heads for Recycle Bin (2013) · Converge Digest
- Public safety interoperability implications of non-P25 radio technologies (July 2016) · DHS Office of Emergency Communications
- Mission critical services · 3GPP
Show all 55 sources
- P25 frequently asked questions, version 1.9 (2025) · P25 Technology Interest Group
- ATIS Telecom Glossary: codec · ATIS
- 47 CFR 2.1047: Measurements required, voice modulated communication equipment · Cornell LII, US Code of Federal Regulations
- 47 CFR 90.209: Bandwidth limitations · Cornell LII, US Code of Federal Regulations
- 47 CFR 2.101: Frequency and wavelength bands · eCFR, US government
- UHF vs VHF · Motorola Solutions
- 47 CFR Part 95, Subpart B: Family Radio Service · eCFR, US government
- Talkabout T802/T803 series user guide (May 2024) · Motorola Solutions
- SmartPTT PLUS dispatch software application · Motorola Solutions application catalog
- JPS NXU-2B Radio over IP (RoIP) gateway datasheet (Rev. 8, 2020) · JPS Interoperability Solutions
- 3G CDMA Network Retirement · Verizon Business
- 1NCE Connect: pricing · 1NCE
- Inrico S100 LTE radio · Passion Radio
- Release 8 · 3GPP
- Mobile roaming costs: roam like at home · Your Europe, European Union
- HD Voice FAQs · Verizon
- Equipment for potentially explosive atmospheres (ATEX) · European Commission
- Creating a Push to Talk app · Apple Developer Documentation
- Charging two-way radios and battery life · Hytera Canada
- Create and monitor geofences · Android Developers
- What is GNSS · EUSPA
- Lone working · Health and Safety Executive, UK
- MIL-STD-810H: environmental engineering considerations and laboratory tests (31 January 2019) · US Department of Defense
- TLK 110 two-way radio · Motorola Solutions
- ACP 125(G): Communications instructions, radiotelephone procedures (28 November 2016) · CCEB (copy hosted by Dalhousie University)
- 47 CFR 97.3: Definitions, Amateur Radio Service · Cornell LII, US Code of Federal Regulations
- 47 CFR Part 95, Subpart D: Citizens Band Radio Service · eCFR, US government
- About GNU Radio · GNU Radio project
