The error rate for the magnetic scanning of a typical cheque is smaller than with optical character recognition systems.
2.
As they went past each house, and picked up the magnetic scanning field or tuner back radiation ( TV users who don't pay the fee tended to use rabbit ears & not an external antenna ), they checked against a list of address who did have licences, When they found an unlicenced address emitting a scanning field, they checked the building plan, which they obtained from local government.
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