Electronic memory for telephone prepaid transaction card - uses encoded memory to validate alteration of credit balance in on-card non-volatile memory

摘要: The prepaid card is of the type having a payment value which reduces with each transaction, and has facilities to modify electronic memory on record balance remaining after transaction. three zones non volatile memory; alterable zone, zone containing an identification number decoding key. A comparator circuit (12) tests result processing by algorithm in reader against code If they correspond allows writing port (13) data are passed (11). When available too low may be restored using device suitable encoding arrangement. system partic. intended for pay phones.