ELECTRICAL PROPERTIES
The electrical properties of smart cards depend solely on the embedded microcontroller, since it is the only component of the card with an electrical circuit. This situation will undoubtedly change in the future with the addition of other components to cards, such as displays, keypads and the like, but it will take some time before these new types of smart cards are widely used. The application that from the very beginning has imposed many rigid requirements on the electrical properties of smart cards is mobile telecommunications using the GSM system. This system, which features an extremely large variety of technically different types of terminal devices made by an equally large variety of manufacturers, which must work with a variety of card types that is at least as large, has for a long time imposed extremely severe requirements. Due to the large number of smart cards used in the GSM system, the electrical characteristics specified for GSM cards have become general guidelines for all manufacturers of smart card
microcontrollers. It can be assumed that nearly all new microcontrollers for smart cards will comply with the general electrical parameters of the relevant GSM specifications, since they otherwise would be practically unsellable in the telecommunications market.

In the early days of smart card technology, quite often the primary considerationwas that the implanted microcontroller was functional, and less attention was paid to its general electrical properties, such as current consumption. At that time, the applications were almost exclusively closed, and they used a single type of card with a terminal specifically designed to match that type of card. The electrical properties of the smart card were relevant only in the sense that they had to be constant, since the terminal was designed to work with a particular type of microcontroller. However, the present situation is completely different.With current large-scale applications, in which various types of smart cards must work together with many different types of terminals, it is an unavoidable requirement that all of the cards that are used are either electrically identical or at least behave uniformly within clearly defined electrical regions. The general international basis for the electrical properties of smart cards is the ISO/IEC
7816-3 standard and its associated amendment (Amd. 1). The amendment will be incorporated into the standard in the next major revision and thus disappear as a separate document.
This standard specifies all of the fundamental electrical requirements for smart cards, such as the voltage ranges, maximum current consumption and the activation and deactivation sequences. As usual with international standards, ISO/IEC 7816-1 provides a range of options that in many cases is too extensive for practical use. This allowed supplementary industry standards to become established in the form of EMV 2000 for financial transactions and GSM 11.11, GSM 11.12, GSM 11.18 and TS 102.221 for telecommunications applications. These industry
standards by no means compete with the ISO/IEC 7816-1 standard, but instead complement it with meaningful restrictions arising from practical smart card applications using millions of issued cards.

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The distinction between smart cards used for financial transactions and smart cards used for telecommunications came about because certain requirements proved to have fundamentally different natures in these two application areas. For example, in the financial transactions area the current consumption and voltage range parameters are fully non-critical, since the terminals used for such applications are connected to the public power network. The situation in the telecommunications area is completely different, since every milliwatt counts when the objective is to achieve the longest possible operating time for a battery-powered mobile telephone. Consequently, the requirements for the least possible current consumption and low supply voltages are highly important in this application area.
Table 3.2 provides a summary of the most important electrical requirements of the essential international standards and industry standards. More detailed information is provided in the following sections.

Table 3.2 Summary of three electrical parameters (voltage, current and clock rate) for the most important international and industrial standards for smart cards. The tolerance ranges for the maximum current can be found in the relevant standards

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