Radio Communications Glossary - Technical Terms Explained

This handy guide will help to explain what some terms used in the world of radios and radio communications actually mean.

Battery Pack
All professional walkie-talkies come with a rechargeable battery pack. It usually makes up the rear of the body of the radio, and can be detached using some kind of catch. Most walkie-talkie battery packs can be charged while attached to the radio or separately, thus allowing users to have spare batteries on charge, ready to be quickly swapped for discharged ones without having to wait for batteries to recharge.
Base Station
The term "base station" refers to a radio that is used from a fixed location, usually using mains electrical power and a permanent or semi-permanent antenna. A base station is often a more powerful radio with longer range than a small, battery powered walkie-talkie. Please do not confuse a "base station" with a walkie-talkie charger unit, as described below.
This is the electrical device into which you place a walkie-talkie to recharge its battery pack. The charger is plugged into a wall socket, and usually consists of a power transformer, and then the actual charging cradle that you place the radio into. Users of larger numbers of walkie-talkies often have multi-slot chargers that can charge six or more radios at one time. Charging usually takes 1-3 hours for a totally discharged battery.
CTCSS (Continuous Tone Controlled Squelch System)
A method of making most use of a given radio channel, where a group of radios are set to transmit an inaudible tone with every transmission, and at the same time to only receive messages with the same tone set. It allows several groups of radio users to make use of the same channel without constantly hearing messages not intended for their group. CTCSS codes are sometime referred to as "privacy codes" and also (somewhat inaccurately) as "sub channels".
FCC (Federal Communications Commission)
The American government organisation that oversees and controls access to the radio airwaves. In the United Kingdom the same role is carried out by OFCOM.
FRS (Family Radio Service)
This is an American government standard for short-range UHF walkie-talkies that can be bought and used in the USA and Canada with no restriction and no licence required. FRS radios have 14 channels, and use frequencies around 462 and 467MHz. The use of FRS radios in the UK and Europe is not legal, although not uncommon, due to people purchasing American radios whilst on holidays and bringing them home, and also buying them online, without realising the legal issues involved.
GMRS (General Mobile Radio Service)
This is an American government standard for UHF walkie-talkies that can be bought and used in the USA and Canada with no restrictions, although a licence is supoosed to be obtained from the FCC (Federal Communications Commission). Radios that combine the FRS (see above) and GMRS channels are widely sold. These have 22 channels in total. They use frequencies around 462 and 467MHz. GMRS radios can have up to 5 watts power output, giving longer ranges than FRS radios. The use of FRS radios in the UK and Europe is not legal, although not uncommon, due to people purchasing American radios whilst on holidays and bringing them home, and also buying them online, without realising the legal issues involved.
IP (Ingress Protection) Ratings
These are an international standard series of protection levels against dirt, dust and liquids getting inside a piece of equipment. The first number relates to solid particle ingress protection, the second to liquid protection. The higher each number, the higher the level of protection provided. For example, IP67 means that the product is completely dustproof and can be immersed in water.
Joint Frequency Management Group (JFMG)
A committee that assigns radio frequencies to different companies and organisations using radio equipment at certain major events where there could be clashes of users of radio frequencies.
Lone Worker
A feature of some walkie-talkies where at certain preset time intervals, the radio user is alerted to press a button to "tell" a control centre that he is OK. If he does not acknowledge the periodic alert by pressing the button, then after another preset time, the radio sends out an alarm message. The purpose of this feature is to protect a person working on their own, so that if someone was to become ill or incapacitated, then their radio would send out an alarm signal that is picked up by someone in a control centre or security office, who can then send help.
A feature of some walkie-talkies, where a tilt-switch inside the radio automatically sends an alarm signal if the radio is tipped on its side for more than a preset period. The radio usually beeps to warn the user that the alarm signal will be sent if the radio is not positioned upright again. The purpose of the "man down" feature is to protect lone workers, so that if someone was to fall, become ill, or be attacked, resulting in them falling down, their radio would send out an alarm signal that is picked up by someone in a control centre or security office, who can then send help.
milliAmp-hours (mAh)
A measure of the storage capacity of a battery. A walkie-talkie's rechargeable battery will typically have a capacity of between 1000 and 2000 milliAmp-hours (mAh). The capacity of a battery pack is usually marked as, for example, 1700mAh.
A charging unit for walkie-talkie radios that allows several walkie-talkies to be charged at the same time. Typically these have six charging slots, although larger multichargers exist. Sometimes these are called "bank chargers".
OFCOM (Office Of Communications)
The government organisation in the United Kingdom responsible for controlling and licencing the use of the airwaves for all types of radio use, including commercial broadcast radio and television, business radio, marine radio, hobby (amateur) "ham" radio, CB radio, etc. Users wanting to apply for business radio licences can do so online at Ofcom's web site.
Phonetic Alphabet
The standard "NATO" phonetic alphabet is a standard list of words used to represent each letter of the alphabet when talking on radios (or on the phone!) especially when the signal is not too clear. Using the phonetic alphabet to spell out names, locations and so on makes accurately understanding messages a lot easier, because many letters can be easily confused when heard over a crackly radio link (P, B, D, T and S, F, etc).
This is a UK (and European Union) standard for basic, short-range radio that can be sold to and used by anyone without the need for any kind of radio licence. Radios that conform to this standard, whatever brand, all must have the same eight channels, and can have a maximum power output of 0.5 watts. They use eight frequencies in the UHF band, around 446MHz, hence the name. Different makes of PMR446 radios should be able to communicate with each other.
PTT (Push To Talk) Button
All walkie-talkie radios have a Push-To-Talk button. This is the button, usually located on the side of the radio, that must be held down to make the radio transmit, and then released when the user has finished transmitting and wishes to listen for messages from other radios. Accessories plugged in to walkie-talkies, such as earpiece/microphones, usually have a second PTT button on the accessory for ease of use.
This is a device that picks up radio messages on one channel, and then simultaneously re-transmits them, usually with more power, on a second channel. Repeaters are used to extend the area of coverage of a group of walkie-talkies or other radios. The repeater (or at least its antennas) is usually located in a high-up position, such as on the roof of a building or on top of a mast, to maximise the range covered.
Roger Beep
A feature of some radios where the radio transmits a "beep" sound when the Push To Talk button is released. This lets the person receiving the transmission know that the sender has finished speaking, and has let go the PTT button. It removes the need for the person transmitting to say "over" to indicate the end of their transmission.
Electronic circuitry in a radio that mutes the radio's speaker if no strong radio signal is being received. If a walkie-talkie did not have a squelch circuit, the speaker would emit a continuous "white noise" hissing sound all the time when no radio message was being received.
A term for any radio that transmits and receives. The term was created by combining the words "transmitter" and "receiver". All walkie-talkies are transceivers.
Two Way Radio
A term for any radio that transmits and receives. It does not mean that only two radios can be used together. A "one way radio" is the kind of radio that is used to listen to broadcast radio stations.
UHF (Ultra High Frequency)
UHF radio signals are those with frequencies from 300Mhz - 3000Mhz. In terms of UK business walkie-talkies, UHF radios use frequencies between 400 - 470MHz. UHF radio signals don't go as far as VHF signals, but are generally better at propagating inside buildings.
VHF (Very High Frequency)
VHF radio signals are those with frequencies from 30MHz - 300MHz. In terms of UK business walkie-talkies, VHF radios use frequencies between 136 - 174MHz. VHF radio signals travel further than UHF signals but do not travel well inside and through buildings.
VOX (Voice Activated Transmit)
A feature of some walkie-talkie radios where the user does not need to press and hold a button to transmit, instead they just speak into the radio, and it transmits for as long as it detects sound above a preset and often adjustable threshold.
Walkie Talkie Radio
Any kind of small, portable battery powered two-way radio. Walkie-talkies are small enough to be held in the user's hand, and carried easily, often clipped to a belt, or in a pocket. Walkie-talkies offer fairly short-range communication, from a few hundred metres to a few miles, depending on power and terrain & buildings between the two radios.
Watts (power output of radio)
The power output of a walkie-talkie or other radio is generally given in watts. The higher the power output, in general, the longer the radios effective range and the better and clearer its signal will be. Most "standard" walkie-talkies have 4 or 5 watts power output. Some have only 0.5 watts to comply with regulations limiting the power output of radios that can be used without any kind of licence. See PMR446 for an example of this.

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