Hand with RFID card books the working time at the INTUS 5540 time recording terminal.

How RFID chips work: Contactless ID cards explained

By: Stefan Erber Created: 28.07.2026

Hold an employee ID card up to the reader – the door opens. Present the card at a terminal – working time is recorded.

In everyday use, RFID cards and key fobs often seem straightforward. What happens in the background, however, usually remains invisible: How does a reader recognize an identification medium? Where does an RFID card get its energy from? And why does the RFID chip itself not decide whether access is granted?

This article provides a clear and practical explanation of how RFID chips work: how RFID identification media are constructed, how communication between the chip and reader takes place, and what role the connected system plays in access control and time and attendance.

What you will learn in this article

Identmedien RFID-Kartenansichten zwei verschiedene Motiven

How is an RFID identification medium constructed?

Whether it is an employee ID card, key fob or RFID tag, the underlying technology is similar. At its core, an RFID identification medium consists of an RFID chip and an antenna. Together, these components form what is known as the RFID inlay.

The RFID chip stores the information required for identification and makes it available during the reading process. The antenna enables data exchange with the RFID reader. In passive RFID media, it also captures energy from the reader’s electromagnetic field, which powers the chip during the reading process.

From RFID inlay to a ready-to-use identification medium

To protect the chip and antenna during everyday use, the inlay is embedded in a card body or housing. This creates a usable identification medium, such as an RFID card, key fob, wristband or specialized RFID tag.

It is important to distinguish between the terms: an RFID chip is not the same as an RFID card. The chip is only one component of a complete identification medium.

Term	Description
RFID chip	Electronic component within the identification medium that stores information and makes it available during the reading process
Antenna	Enables passive media to receive energy and supports data transmission
Inlay	Technical assembly consisting of an RFID chip and antenna
Transponder / RFID tag	Functional unit consisting of an RFID chip and antenna that communicates with an RFID reader. It may be embedded in a card, key fob, wristband or another form factor.
RFID card	Card-shaped form of an RFID identification medium
Identification medium	Umbrella term for RFID cards, key fobs, wristbands and other form factors

How does RFID work step by step?

RFID works through a sequence of coordinated steps involving the identification medium, RFID reader and connected system.

RFID process step 1: The transponder enters the reader’s electromagnetic field.

As soon as an RFID card or another identification medium enters the reading range of an RFID reader, communication can begin. The reader generates an electromagnetic field that enables the reading process.

RFID process step 2: The chip inside the transponder is activated by the reader’s field.

Many RFID identification media do not rely on a battery for power. Instead, the antenna captures energy from the RFID reader’s electromagnetic field and transfers it to the RFID chip. This activates the chip for the duration of the reading process.

RFID process step 3: The activated chip provides the stored identification data.

Once activated, the RFID chip provides the identification data required for the specific application. This may include a credential identifier or other technical information made available by the identification medium during the reading process.

RFID process step 4: The reader receives the identification data from the RFID transponder.

The RFID reader receives the data from the identification medium and prepares it for further processing. The information processed depends on the chip technology used, the application and the system architecture.

RFID process step 5: The reader transmits the identification data to the connected system.

The RFID reader forwards the captured information to the relevant system. Depending on the application, this may be an access control system, a time and attendance system or a controller. The data is then processed there according to the specific application.

RFID process step 6: The system checks authorization and triggers the appropriate action.

In an access control system, the information read from the identification medium is matched to a corresponding record and the stored access rights are checked. If access is authorized, the relevant door is unlocked. If the identification medium is not assigned, has been blocked or is not authorized for that area, the door remains locked.

Are you planning an RFID migration project?

PCS supports companies in selecting, integrating and migrating to suitable RFID identification media for access control and time and attendance.

What information is stored on RFID identification media?

Depending on the chip technology and system architecture, RFID identification media can store different types of information. It is important to distinguish between information stored on the medium and data that is actually processed during a specific reading operation.

Not all stored information is automatically transmitted whenever the identification medium interacts with an RFID reader. The data used depends on the application and system architecture.

Type of information	Possible function
Card or credential identifier	Links the identification medium to a corresponding record
Application-specific data	Used within access control or time and attendance systems
Updatable data	Stores information that can be modified by read/write systems
Technical information	Supports the identification and management of the identification medium within the relevant system

Why is an identifier not the same as access authorization?

What the identifier means

An identifier stored on the medium does not automatically constitute access authorization.
The identifier is initially used to link an identification medium to a record in the system.
The information actually used depends on the chip technology, application and system architecture.
The connected system determines whether to grant access, record a time transaction or trigger another action based on the configured permissions and rules.

What determines the security of an RFID system?

The security level of an RFID system does not depend solely on the identification medium. Key factors include:

the chip technology used,
the system architecture,
security mechanisms such as encryption,
secure key management,
access authorization frameworks, and
organizational processes for managing and blocking identification media.

Why is an RFID card sometimes not recognized?

A failed time recording or access attempt does not necessarily mean that the RFID identification medium is defective. Whether an RFID card is recognized reliably depends on several factors, from the reader’s field and the technology used to the system configuration.

Common causes

Outside the reader’s field: The identification medium is outside the intended reading range or is held near the reader for too short a time.
Incompatible technology: The RFID medium and reader use different technologies, frequencies or communication standards.
Damaged identification medium: The RFID chip, antenna or card body may have been damaged by mechanical stress.
Interference from the environment or surrounding materials: Metal, liquids or electromagnetic interference can disrupt communication between the identification medium and the reader.
Blocked or unassigned identifier: The medium is recognized technically but has been deactivated or blocked in the system, or is not linked to a valid record.
Missing authorization: The medium is recognized but does not have valid authorization for the requested action.

It is important to note that if an RFID card is not recognized or no action is triggered, the RFID chip itself is not always the cause. The reading range, compatibility, condition of the identification medium, system configuration and stored access rights may also play a role.

Key components for RFID applications

For RFID to function reliably in access control or time and attendance systems, identification media, readers and connected systems must be properly aligned. The following components support organizations in selecting, integrating and modernizing their RFID infrastructure.

Identification media

Identmedien Karten und Tags verschiedene Ausführungen

PCS offers a wide range of RFID cards and transponders for time and attendance and access control.

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Access reader

Zutrittsleser INTUS 700touch in Frondansicht

We offer the right access readers for every installation type and application.

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Door terminals & door cylinders

Digitalzylinder INTUS Flex schräge Ansicht

With INTUS Flex, we offer versatile mechatronic locking systems.

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DEXIOS

DEXIOS is our modern software solution for time tracking and access control.

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Time recording terminals

Zutrittskontrollmanager INTUS ACM80e Produktansicht

Modern technology and a customizable interface.

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Conclusion: RFID relies on the interaction between the identification medium, reader and system

RFID chips store the identification information required for a specific application and make it available during the reading process. With passive identification media, the electromagnetic field generated by the RFID reader supplies the necessary energy. The reader captures the information and forwards it to the connected system.

Application-specific processing takes place only within that system. An access control system, for example, checks the relevant authorization before unlocking a door, while a time and attendance system assigns the data to a time transaction. The decisive factor is therefore not the RFID chip alone, but the interaction between the identification medium, reader and connected system.