IEC 62055-51:2007

Electricity metering - Payment systems - Part 51: Standard transfer specification (STS) - Physical layer protocol for one-way numeric and magnetic card token carriers

specifies a physical layer protocol of the standard transfer specification (STS) for transferring units of credit and other management information between a point-of-sale (POS) system and an STS-compliant electricity payment meter.

General Information

• Status: Published
• Publication Date: 22-May-2007
• ICS: 35.100.10 - Physical layer
• ICS: 91.140.50 - Electricity supply systems
• Technical Committee: TC 13 - Electrical energy measurement and control
• Drafting Committee: WG 15 - TC 13/WG 15
• Current Stage: PPUB - Publication issued
• Start Date: 31-Aug-2007
• Completion Date: 23-May-2007

Overview

IEC 62055-51:2007 defines the physical layer protocol of the Standard Transfer Specification (STS) for one‑way numeric and magnetic card token carriers used in electricity metering payment systems. The standard specifies how units of credit and management information are encoded at a point‑of‑sale (POS) and decoded by STS‑compliant payment meters. It is part of the IEC 62055 series that establishes interoperable, secure token-based vending for utilities.

Key topics

• Scope of the physical layer: Encoding and decoding rules for token data exchanged between POS systems and payment meters using one‑way token carriers (magnetic cards and numeric token carriers).
• TokenCarrierDataUnit (TCDU): Defines the data elements and structure that must be carried on token media for reliable transfer of credit and management messages.
• Magnetic card encoding: Rules for formatting STS tokens on magnetic stripe tracks (references ISO/IEC 7811/7813 standards).
• Numeric token encoding: Rules for representing token data as numeric tokens (decimal representations and conversions used by meters).
• Interoperability and procurement: Guidance (including Annex A) on selective compliance and procurement options so buyers and manufacturers can ensure compatibility.
• Security and key management: STS framework provides secure message formats and cryptographic key management practices (see IEC 62055-41 for application‑layer security details).
• Normative references: Cross‑references to IEC 62055‑41 (application layer), IEC 62055‑31 (meter requirements) and ISO/IEC identification card standards.

Note: the standard records that some numeric token carrier techniques may be subject to patent rights; licensing information is registered with the IEC.

Applications

• Electricity utilities: Enabling interoperable vending of prepaid credit across multiple POS vendors and meter manufacturers.
• Meter manufacturers: Implementing STS‑compliant decoders to accept magnetic and numeric tokens in payment meters.
• POS and vending equipment vendors: Encoding STS tokens correctly onto magnetic cards or printing numeric token carriers for sale to customers.
• Other utilities: Adaptable for prepaid systems for water and gas where token‑based prepayment is used.

Practical benefits include vendor interoperability, consistent token formatting, standardized POS‑to‑meter communication, and clearer procurement specifications for utilities and integrators.

Related standards

• IEC 62055‑41 - STS application layer protocol for one‑way token carriers (security, message types)
• IEC 62055‑31 - Particular requirements for static payment meters
• IEC 62051 - Electricity metering glossary
• ISO/IEC 7810, 7811‑2, 7813 - Identification card physical and magnetic stripe standards

Implementers should read IEC 62055‑51 together with IEC 62055‑41 for the complete STS message and security context.

Standards Content (Sample)

INTERNATIONAL IEC
STANDARD 62055-51
First edition
2007-05
Electricity metering – Payment systems –
Part 51:
Standard transfer specification (STS) –
Physical layer protocol for one-way numeric
and magnetic card token carriers

Reference number
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INTERNATIONAL IEC
STANDARD 62055-51
First edition
2007-05
Electricity metering – Payment systems –
Part 51:
Standard transfer specification (STS) –
Physical layer protocol for one-way numeric
and magnetic card token carriers

PRICE CODE
Commission Electrotechnique Internationale S
International Electrotechnical Commission
МеждународнаяЭлектротехническаяКомиссия
For price, see current catalogue

– 2 – 62055-51 © IEC:2007(E)
CONTENTS
FOREWORD.3
INTRODUCTION.5

1 Scope.6
2 Normative references .6
3 Terms, definitions and abbreviations .7
3.1 Terms and definitions .7
3.2 Abbreviations .7
3.3 Notation and terminology.8
3.4 Numbering conventions .8
4 STS protocol reference model .9
5 POSToTokenCarrierInterface: Physical layer protocol .10
5.1 TCDU .10
5.2 Magnetic card token carrier .11
5.3 Numeric token carrier .15
6 TokenCarrierToMeterInterface: Physical layer protocol.17
6.1 TCDU .17
6.2 Magnetic card token carrier .17
6.3 Numeric token carrier .18

Annex A (informative) Procurement options for users of STS-compliant systems .20

Bibliography.21

Table 1 – Data elements in the TCDU .10
Table 2 – Data elements in the IDRecord.10
Table 3 – Mandatory data fields for Record1 to be encoded on Track 3 .13
Table 4 – Separator data field to be encoded on Track 3 with optional Record2.13
Table 5 – Data fields for optional Record2 to be encoded on Track 3.13
Table 6 – Example of 66-bit binary to 20-digit decimal conversion .16
Table 7 – Data elements in the TCDU .17
Table 8 – Example of a 20-digit decimal to 66-bit binary conversion .19
Table A.1 – Items that should be noted in purchase orders and tenders.20

Figure 1 – Physical layers of the STS protocol stack.9

62055-51 © IEC:2007(E) – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
_____________
METERING – PAYMENT SYSTEMS –
Part 51: Standard transfer specification (STS) –
Physical layer protocol for one-way numeric
and magnetic card token carriers

FOREWORD
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
The International Electrotechnical Commission draws attention to the fact that it is claimed that compliance with
this document may involve the use of patents concerning the numeric token carrier given in 5.3 and 6.3.
The IEC takes no position concerning the evidence, validity and scope of these patent rights. The holder of these
patent rights has assured the IEC that he is willing to negotiate licences under reasonable and non-discriminatory
terms and conditions with applicants throughout the world. In this respect, the statements of the holders of these
patents are registered with the IEC. Information may be obtained from:
Address: Meter Patents Development (Pty) Ltd, c/o Spescom Limited – Head Office, P.O. Box 288,
Halfway House 1685, South Africa.
Tel: [phone]
Fax: [phone]
Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights other than those identified above. IEC shall not be held responsible for identifying any or all such patent
rights.
International Standard IEC 62055-51 has been prepared by working group 15, of IEC
technical committee 13: Electrical energy measurement, tariff and load control.
IEC 62055-51 is complementary to, and is to be read in conjunction with, IEC 62055-41.

– 4 – 62055-51 © IEC:2007(E)
The text of this standard is based on the following documents:
CDV Report on voting
13/1406/CDV 13/1410/RVC
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

62055-51 © IEC:2007(E) – 5 –
INTRODUCTION
The IEC 62055 series covers payment systems, encompassing the customer information
systems, point of sales systems, token carriers, payment meters and the respective interfaces
that exist between these entities. At the time of preparation of this part, IEC 62055 comprised
the following parts, under the general title Electricity metering – Payment systems:
Part 21: Framework for standardization
Part 31: Particular requirements – Static payment meters for active energy (classes 1 and 2)
Part 41: Standard transfer specification – Application layer protocol for one-way token
carrier systems
Part 51: Standard transfer specification – Physical layer protocol for one-way numeric and
magnetic card token carriers
Part 52: Standard transfer specification – Physical layer protocol for a two-way virtual token
carrier for direct local connection
The Part 4x series specifies application layer protocols and the Part 5x series specifies
physical layer protocols.
The standard transfer specification (STS) is a secure message protocol that allows
information to be carried between point-of-sale (POS) equipment and payment meters and
caters for several message types such as credit, configuration control, display, and test
instructions. It further specifies devices and codes of practice that allow for the secure
management (generation, storage, retrieval and transportation) of cryptographic keys used
within the system.
The national electricity utility in South Africa (Eskom) first developed and published the STS
in 1993 and transferred ownership to the STS Association in 1998 for management and
further development.
Prior to the development of the STS a variety of proprietary payment meters and POS
equipment had been developed, which were, however, not compatible with each other. This
gave rise to a definite need among the major users to move towards standardized solutions in
addressing operational problems experienced where various types of payment meter and POS
equipment had to be operated simultaneously. An STS was developed that would allow for the
application and inter-operability of payment meters and POS equipment from multiple
manufacturers in a payment metering installation.
The TokenCarrier is the physical device or medium used to transport the information from the
vending system to the payment meter. Two types of token carriers are specified in this part of
IEC 62055, a magnetic card and a numeric token carrier, which have been approved by the
STS Association. New token carriers can be proposed as new work items through the National
Committees or through the STS Association.
Although the main implementation of the STS is in the electricity supply industry, it inherently
provides for the management of other utility services like water and gas. Future revisions of
the STS may allow for other token carrier technologies like smart cards and memory keys with
two-way functionality and to cater for a real-time clock and complex tariffs in the payment
meter.
The STS Association has established a D-type liaison with working group 15 of IEC TC 13 for
the development of standards within the scope of the STS and is thus responsible for the
maintenance of any such IEC standards that might be developed as a result of this liaison.
The STS Association is also registered with the IEC as a Registration Authority for providing
maintenance services in support of the STS (see Clause C.1 of IEC 62055-41 for more
information).
– 6 – 62055-51 © IEC:2007(E)
ELECTRICITY METERING – PAYMENT SYSTEMS –

Part 51: Standard transfer specification (STS) –
Physical layer protocol for one-way numeric
and magnetic card token carriers

1 Scope
This part of IEC 62055 specifies a physical layer protocol of the standard transfer
specification (STS) for transferring units of credit and other management information between
a point-of-sale (POS) system and an STS-compliant electricity payment meter.
It specifies
• encoding of token data onto token carriers in the physical layer protocol at the POS for
various TokenCarrierTypes such as numeric and magnetic cards;
• decoding of token data from token carriers in the physical layer protocol at the payment
meter for various TokenCarrierTypes such as numeric and magnetic cards.
It is intended for use by manufacturers of payment meters that have to accept tokens that
comply with the STS, and also by manufacturers of POS systems that have to produce STS-
compliant tokens, and should be read in conjunction with IEC 62055-41.
NOTE 1 Although developed for payment systems for electricity, the standard also covers tokens used in other
utility services, such as water and gas.
NOTE 2 STS-compliant products are required to comply with selective parts of this International Standard only,
which should be the subject of the purchase contract (see Annex A).
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60050-300, International Electrotechnical Vocabulary – Electrical and electronic measure-
ments and measuring instruments – Part 311: General terms relating to measurements – Part
312: General terms relating to electrical measurements – Part 313: Types of electrical
measuring instruments – Part 314: Specific terms according to the type of instrument
IEC 62051, Electricity metering – Glossary of terms
IEC 62055-31:2005, Electricity metering – Payment systems – Part 31: Particular
requirements – Static payment meters for active energy (classes 1 and 2)
IEC 62055-41, Electricity metering – Payment systems – Part 41: Standard transfer
specification – Application layer protocol for one-way token carrier systems
ISO/IEC 7810:2003, Identification cards – Physical characteristics
ISO/IEC 7811-2:2001, Identification cards – Recording technique – Part 2: Magnetic stripe –
Low coercivity
ISO/IEC 7813:2006, Information technology – Identification cards – Financial transaction
cards
62055-51 © IEC:2007(E) – 7 –
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-300,
IEC 62051, IEC 62055-31, IEC 62055-41 apply.
3.2 Abbreviations
ANSI American National Standards Institute
APDU ApplicationProtocolDataUnit
ASCII American Standard Code for Information Interchange
DOE DateOfExpiry
DD Discretionary Data
EA EncryptionAlgorithm
ED ExpirationDate
ETX ASCII End Of Text character
FS FieldSeparator
ID Identification; Identifier
ISO International Standards Organization
KRN KeyRevisionNumber
LRC LongitudinalRedundancyCheck
OSI Open Systems Interconnection
PAN PrimaryAccountNumber
POS PointOfSale
PRN Printer
PSTN Public Switched Telephone Network
SC ServiceCode
SGC SupplyGroupCode
STS Standard Transfer Specification
STX ASCII Start of Text character
TCDU TokenCarrierDataUnit
TCT TokenCarrierType
TI TariffIndex
– 8 – 62055-51 © IEC:2007(E)
3.3 Notation and terminology
Throughout this standard the following rules are observed regarding the naming of terms.
• Entity names, data element names, function names and process names are treated as
generic object classes and are given names in terms of phrases in which the words are
capitalized and joined without spaces. Examples are: SupplyGroupCode as a data element
name, EncryptionAlgorithm07 as a function name and TransferCredit as a process name
(see note).
• Direct (specific) reference to a named class of object uses the capitalized form, while
general (non-specific) reference uses the conventional text i.e. lower case form with
spaces. An example of a direct reference is: “The SupplyGroupCode is linked to a group of
meters”, while an example of a general reference is: “A supply group code links to a
vending key”.
• Other terms use the generally accepted abbreviated forms like PSTN for Public Switched
Telephone Network.
NOTE The notation used for the naming of objects has been aligned with the so-called “camel-notation” used in
the common information model (CIM) standards prepared by TC 57, in order to facilitate future harmonization and
integration of payment system standards with the CIM standards.
3.4 Numbering conventions
In this standard, the representation of numbers in binary strings uses the convention that the
least significant bit is to the right and the most significant bit is to the left.
Numbering of bit positions start with bit position 0, which corresponds to the least significant
bit of a binary number.
Numbers are generally in decimal format, unless otherwise indicated. Any digit without an
indicator signifies decimal format.
Binary digit values range from 0-1.
Decimal digit values range from 0-9.
Hexadecimal digit values range from 0-9, A-F and are indicated by “hex”.

62055-51 © IEC:2007(E) – 9 –
4 STS protocol reference model

POS METER
Application Application MeterFunctionObjects
Process Process
Companion Specifications
Key Management
APDU APDU
Application Layer Application Layer
Protocol Protocol
5.1 6.1
TCDU TCDU
Physical Layer Physical Layer
Protocol Protocol
5.2 6.2
5.3 6.3
Token Carrier
POSToTokenCarrierInterface TokenCarrierToMeterInterface
IEC  574/07
Key
APDU ApplicationLayerDataUnit; data interface to the application layer protocol
TCDU TokenCarrierDataUnit; data interface to the physical layer protocol
Relevant clause number references in this standard are indicated adjacent to each box

Figure 1 – Physical layers of the STS protocol stack
The STS is a secure data transfer protocol between a POS and a payment meter using a
token carrier as the transfer medium. The application layer protocol deals with tokens and
encryption processes and functions and is specified in IEC 62055-41, while the physical layer
protocol deals with the actual encoding of the token data onto various types of token carriers
(see Figure 1).
This standard specifies a physical layer protocol that deals with the actual encoding of the
token data onto a numeric token carrier and a magnetic card token carrier and operates in
conjunction with the application layer protocol specified in IEC 62055-41.
Examples of other types of physically transportable token carrier devices are: numeric,
magnetic cards, memory cards and memory keys, which might be specified in future in other
parts of the IEC 62055-5x series.
A more complete description of the STS refere
...