Proximity card

The term "proximity card" refers to the older 125 kHz devices as distinct from the newer 13.56 MHz contactless smartcards.

[1][2] Passive cards have three components which are sealed inside the plastic: an antenna consisting of a coil of wire, a capacitor, and an integrated circuit (IC) which contains the user's ID number in specific formats and no other data.

The chip sends its ID number or other data to the antenna coil, which transmits it by radio frequency signals back to the reader unit.

The battery also powers a transmitter circuit in the chip which transmits a stronger return signal to cover the greater distance.

These standards define two types of card ("A" and "B", each with different communications protocols) which typically have a range up to 10 cm (4 in).

The related ISO/IEC 15693 (vicinity card) standard typically works up to a longer range of 100 centimetres (39 in).

The best way to check if a technology meets ISO standard is to ask the manufacturer if it can be emulated on other devices without any proprietary hardware.

For smartcards, a numbering system is internationally harmonized and allocated by Netherlands-based NEN (registration authority) according to ISO/IEC 6523 and ISO/IEC 15459 standards.