Comms: a new use for a biscuit tin

When people walk into a meeting, they are used to being told to turn their phones to silent, or even to aeroplane mode. Some are used to being told to turn them off and some - in extreme cases, to deposit them either on a side table or with a clerk.At some buildings that are paranoid, phones must be deposited with the security guard at the gate.

But German chemical company Evonik has taken a new approach with a new use for an old biscuit tin. A report that started people thinking it was joke has been followed up by AFP (a news agency) and the company has confirmed something strange. Like most meeting rooms, those at the company come with table, chairs, lights, pens, paper, drinking water, some kind of A/V equipment. But the biscuits are on a plate, not in the tin that site prominently in the room.

That tin is reserved - and those attending meetings are required to put their phones into it on arrival, even if they are turned off.

The concern is that many phones (either by design or by the use of downloaded "apps" do not turn off completely - as smart-phones become PDAs, they remain partially alert so as to deliver alarm calls, etc. If the phone gives all the appearances of being "off" but it is still - on some level - operational what, other than the alarm clock - might it be doing?

Evonik is concerned by rumours that the phone might be used as a bug - listening to conversations and transmitting the data live. Speculating, it seems they have decided that the RAM in a phone is not enough to store the data for later replay.

The theory, then, is that by putting the phone into a metal box, its communications ability will be neutralised.

Nice try, but it doesn't work. Or, rather, it doesn't work with all biscuit tins. The Register tested a McVities Biscuit Assortment tin and found it was hopeless for blocking 3G and GSM signals while a (UK issue) Jacobs' Cream Crackers (don't laugh - it's not rhyming slang) tins worked.

We tried our own test: a large tea tin from a small tea shop in Wanchai had a barely noticeable effect on the ability of various Nokia, HTC, Samsung and Apple phones - beyond making what the phone "heard" fuzzy. But a smaller (and much thicker) tea tin from a tea shop in Tsim Sha Tsui rendered several of the phones incommunicado.

But the best thing, it turns out, was to try to use the phone in the 36th floor of an apartment block where the cell towers are obscured by other buildings and by height. Or even some hotel rooms in older, denser hotels such as several in New York.

However, the tin thing isn't entirely useless: radio signals depend on frequency (duh!) and the thickness of the tin and the metal it is made of do make a difference. Steel seems to be best (hence problems in steel-framed buildings) and aluminium least effective. Fill the tin with foam to reduce sound transmission in the first place and the idea starts to look a lot less bizarre.

But that still leaves out the question of blue tooth where the mic can be obscured anywhere and the phone set to record.

These issues are probably pointless to try to combat: why bother with all of that complex and potentially unreliable tech when it's far easier to use a recorder masquerading as a pen or a USB stick? At least, with the prevalence of non-smoking offices, the old standby of a packet of cigarettes tossed onto the table now looks suspicious.