25 AUGUST 1984, Page 17

How to phone-tap

Sir: Paul Johnson (The press, 18 August) is a little out of date when he says that 'Phone-tapping, in practice, is virtually confined to government and its agencies.' He is no doubt thinking of the time when Phone-tapping equipment was bulky and expensive. Today, cheap phone-tapping 'bugs' can be bought in gadget shops, and they are openly advertised in Exchange and Mart.

Suppose that I wished to plant a bug on Mr Johnson's phone. I would follow the technique laid down in John Wingfield's excellent book Bugging: A Complete Sur- vey of Electronic Surveillance Today, and would act as follows: Pretending to be a stranded motorist, I would call at Mr Johnson's house. 'Oh, sir,' I would say. 'My car's broken down, and my wife' will be desperately anxious about me. May I use your phone?' He, out of politeness, would no doubt leave me alone in his study to make the call. As soon he was gone, I would unscrew the mouth- piece of his phone and implant the bug, a device about half the size of a sugar cube. From that moment on, I could listen to his telephone calls whenever I wished to. Adrian Berry

Science Correspondent,

Daily Telegraph, 135 Fleet Street, London EC4