A multiple rate metering system suitable for use with an existing single rate, electromechanical electricity meter employing an Eddy current disc mounted in a casing, comprises a first unit mountable inside the casing of the electricity meter, and a second unit, which is portable so that it can be brought...http://www.google.com.au/patents/US4516213?utm_source=gb-gplus-sharePatent US4516213 - Multiple rate metering system
