ENGINEERS in Britain who have spent the past two years developing a hand-held
device to detect illicit TV sets will soon be overtaken by changing technology.
While their detector is great at spotting the radio frequencies emitted by the
cathode-ray tubes used in conventional sets, it is blind to the new flat-panel
displays.
Some 24 million British households pay the annual 拢97.50 TV licence
fee, which raises around 拢2 billion for the BBC to pay for its TV and
radio broadcasts. TV Licensing, based in Bristol, has the task of collecting
this money. Every year, 400 000 people who use their TV without a licence are
caught and fined up to 拢1000, but a hard core of nearly 2 million still
watch TV without paying up. It is to catch these freeloaders that TV Licensing
has spent time and effort developing its new device.
Since 1952, attempts to track down licence dodgers have relied on detector
vans fitted with directional aerials that tour the streets, looking for the
stray signals emitted by TV sets鈥� tuning circuits. The late MI5 operative Peter
Wright revealed in his book Spycatcher that British intelligence used
the same technology to find clandestine spy receivers.
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This is fine for picking up sets in ordinary houses, but a van in the street
cannot pinpoint sets in a block of flats. So in 1989, TV Licensing equipped its
staff with a portable version, but this was not sensitive enough to work well.
Determined evaders can screen their sets to reduce signal leakage. So in
鈥減reparation for the digital revolution鈥�, TV Licensing鈥檚 research department has
developed a system that does not rely on stray tuner signals.
Instead, the new device looks for the magnetic component of the emissions
from the scan coils on the TV tube. These coils are pulsed to steer the electron
beam across the screen in a sequence of lines to trace the TV picture. Because
the scan and pulse rate is fixed for Britain鈥檚 625-line TV standard, the
detector can filter out the magnetic fields from other domestic sources such as
washing-machine motors and microwave ovens. A pair of loop aerials, spread out
like small wings, can register the direction of a TV set up to 30 metres away
behind closed doors.
But the device can only detect sets that have a scanning electron beam and
magnetic coils. Flat-panel TVs, LCD projectors or laptop PCs with a TV tuner
will go undetected.
Electronics companies are already selling plasma LCD screens, and are racing
to drive down their price. At the Japan Electronics Show in Osaka in October,
most manufacturers were showing middle-sized LCD TVs, and table-top projectors
that shine light through a small LCD onto a larger screen.
The president of the electronics company and TV manufacturer Sharp, Katsuhiko
Machida, says he wants to 鈥渃onvert all TVs which now use cathode-ray tubes, to
尝颁顿蝉鈥�. He predicts that 鈥渂y the year 2005, all TVs made by Sharp will be using
尝颁顿蝉鈥�.
Simon Ablitt, TV Licensing鈥檚 director of field operations, admits that his
new detector will not detect flat-panel sets. 鈥淲e are keeping tabs on how TV is
developing,鈥� he assures New 杏吧原创.