PEOPLE who buy good quality wireless headphones will no longer be breaking the law in Britain, following a Europe-wide agreement on radio frequencies for headphone use.
The headphones, which let people listen to their stereos around the house without trailing wires everywhere, have been available in the shops for a while. But some use 433 megahertz, a frequency already taken by amateur radio hams, the Ministry of Defence, home security systems and car alarms. To avoid the risk of interference, headphones on this frequency are illegal in Britain (Technology, 11 January, p 19). Legal headphones use a narrow frequency band around 49 megahertz, but the sound quality and range is limited.
Now, after 18 months of research, the European Telecommunications Standards Institute (ETSI) has freed a slice of the spectrum 1 megahertz wide from 863 to 864 megahertz鈥攚ide enough for stereo. The same frequencies will be used across Europe.
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鈥淚t鈥檚 fantastic news,鈥� says Steve Holmes of Vivanco, which makes wireless headphones. 鈥淲e hope to be selling radio headphones for 拢80 and speakers for 拢100 in time for Christmas.鈥� Britain will be the first to free the frequency once the Department of Trade and Industry has made a formal announcement.
The new pan-European band is split into twelve 300-kilohertz channels. Each is wide enough to carry FM stereo of broadcast quality. Neighbours can choose different channels to avoid interfering with each other鈥檚 listening. The transmitter鈥檚 power is limited to 10 milliwatts. Tests run by Vivanco show this is strong enough to cut through walls and broadcast up to 150 metres.