In telecommunication

Telecommunication

Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...

, a low-power communication device, also short-range device (SRD) is a restricted radiation

Radiation

In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

 device, exclusive of those employing conducted or guided radio frequency

Radio frequency

Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...

 techniques, used for the transmission

Transmission (telecommunications)

Transmission, in telecommunications, is the process of sending, propagating and receiving an analogue or digital information signal over a physical point-to-point or point-to-multipoint transmission medium, either wired, optical fiber or wireless...

 of signs, signals (including control signals), writing, images and sounds or intelligence of any nature by radiation of electromagnetic energy. Examples: Wireless microphone, phonograph oscillator

Electronic oscillator

An electronic oscillator is an electronic circuit that produces a repetitive electronic signal, often a sine wave or a square wave. They are widely used in innumerable electronic devices...

, radio-controlled garage door opener

Garage door opener

A garage door opener is a motorized device that opens and closes garage doors. Most are controlled by switches on the garage wall, as well as by remote controls carried in the garage owner's cars, or more rarely, on keychains.- The electric opener :...

, and radio-controlled models.

Low Power Device 433 MHz (LPD433) transceiver

Transceiver

A transceiver is a device comprising both a transmitter and a receiver which are combined and share common circuitry or a single housing. When no circuitry is common between transmit and receive functions, the device is a transmitter-receiver. The term originated in the early 1920s...

 radios are short range, licence free communication devices authorized for use in many parts of the world. In some countries, however, voice is not allowed over LPD. They operate in the UHF

Ultra high frequency

Ultra-High Frequency designates the ITU Radio frequency range of electromagnetic waves between 300 MHz and 3 GHz , also known as the decimetre band or decimetre wave as the wavelengths range from one to ten decimetres...

 band from 433.075 MHz to 434.775 MHz with 25 kHz channel spacing, for a total of 69 channels. These devices are frequency modulated

Frequency modulation

In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...

 (FM) with a maximum legal power output of 10 mW. LPD devices must only be used with the integral and non-removable antenna

Antenna (radio)

An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...

. LPD was introduced to reduce the burden on the eight PMR446

PMR446

PMR446 is a part of the UHF radio frequency range that is open without licensing for personal usage in most countries of the European Union. It has roughly the same use as FRS or GMRS in the United States and Canada. Depending on surrounding terrain range can vary from a few hundred metres to a...

 channels over shorter ranges (less than 1 km) . Channels 1 to 14 are UK Amateur repeater outputs and channels 62 to 69 are UK Amateur repeater inputs.

Channel	Frequency (MHz)	Channel	Frequency (MHz)	Channel	Frequency (MHz)
1	433.075	24	433.650	47	434.225
2	433.100	25	433.675	48	434.250
3	433.125	26	433.700	49	434.275
4	433.150	27	433.725	50	434.300
5	433.175	28	433.750	51	434.325
6	433.200	29	433.775	52	434.350
7	433.225	30	433.800	53	434.375
8	433.250	31	433.825	54	434.400
9	433.275	32	433.850	55	434.425
10	433.300	33	433.875	56	434.450
11	433.325	34	433.900	57	434.475
12	433.350	35	433.925	58	434.500
13	433.375	36	433.950	59	434.525
14	433.400	37	433.975	60	434.550
15	433.425	38	434.000	61	434.575
16	433.450	39	434.025	62	434.600
17	433.475	40	434.050	63	434.625
18	433.500	41	434.075	64	434.650
19	433.525	42	434.100	65	434.675
20	433.550	43	434.125	66	434.700
21	433.575	44	434.150	67	434.725
22	433.600	45	434.175	68	434.750
23	433.625	46	434.200	69	434.775

In ITU region 2 (the Americas), the frequencies that LPD433 uses are within a band allocated to amateur radio

Amateur radio

Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...

. In the United States LPD433 radios can only be used under FCC amateur regulations by properly licenced amateur radio operators. The conflicting allocations have been something of a nuisance to US amateur operators due to use of the equipment by European tourists in the U.S.

European licence-free LPD transceivers also include Short Range Device 860 MHz (SRD860), which have a maximum legal power output of 5 mW. SRD has a total of 126 channels in five bands.

Band A	868.00625 MHz -> 868.59375 MHz	48 Channels
Band B	868.70625 MHz -> 869.19375 MHz	40 Channels
Band C	869.41250 MHz -> 869.63750 MHz	10 Channels
Band C2	869.31250 MHz -> 869.38750 MHz	4 Channels
Band D	869.70625 MHz -> 869.99375 MHz	24 Channels