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Order a copy of the STS Specification from the IEC
IEC 62055-41 : ELECTRICITY METERING – PAYMENT SYSTEMS – Part 41: Standard transfer specification (STS) – Application layer protocol for one-way token carrier systems
IEC 62055-51 : ELECTRICITY METERING – PAYMENT SYSTEMS – Part 51: Standard transfer specification (STS) – Physical layer protocol for one-way numeric and magnetic card token carriers
IEC 62055-52 : ELECTRICITY METERING – PAYMENT SYSTEMS – Part 52: Standard transfer specification (STS) – Physical layer protocol for a two-way virtual token carrier for direct local connection
These standards have now been published by the IEC as international standards and are available from the IEC Webstore in Geneva