You obviously not seen the design to make a Nokia 3310 into a Cellphone
jammer. - Simple sweep osillator curcuit built on veroboard into the
battery compartment ? Just plug the mains addaptor into a stangard 240v
13A GNER/VIRGIN power outlet and enjoy hours of
non-mobile-phone-interrupted-journey.
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For US based readers of this NG : GNER= Great North East Railways . VIRGIN
= Virgin Trains (from the same stock as Virgin Atlantic)
The trains running from London - Edinburgh -Aberdeen vv apparently have
240V-AC sockets for hooking up laptops and other electrical devices.

Frank GM0CSZ / KN6WH