In telecommunication, a low-power communication device, also short range device (SRD) is a restricted radiation device, exclusive of those employing conducted or guided radio frequency techniques, used for the transmission 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, radio-controlled garage door opener, and radio-controlled models.
Low Power Device 433 MHz (LPD433) transceiver radios are short range, licence free communication devices used throughout the world. In some states however voice is not allowed over LPD. They operate in the UHF 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 (FM) with a maximum legal power output of 10 mW. LPD devices must only be used with the integral and non-removable antenna. LPD was introduced to reduce the burden on the eight PMR446 channels over shorter ranges (less than 1 km).
LPD433 usage is not legal in the United States without a licence. This is because the standard allocation is within the range of the 420-450MHz band allocated to US amateur radio operators. 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. Channels 1 to 14 are UK Amateur repeater outputs and channels 62 to 69 are UK Amateur repeater inputs.
Full article ▸