How RFID and NFC Cards Work — A Simple Explanation

What Is RFID?

RFID stands for Radio Frequency Identification. An RFID card contains a tiny microchip and an antenna — both embedded inside the PVC card and invisible from the outside. The chip stores a unique identifier (UID). When the card is brought near an RFID reader, the reader transmits a radio signal, the card's antenna harvests enough energy from that signal to power the chip, and the chip transmits its UID back to the reader — all without any battery or physical contact.

This is called a passive RFID system — the card has no battery and only activates when it is within range of a reader. The entire exchange happens in milliseconds.

What Frequency? The Difference Between 125 kHz and 13.56 MHz

RFID cards operate at two main frequency ranges in India. Low-frequency (LF) cards operate at 125 kHz — these are the older EM4100 and HID Prox cards common in older access control systems. High-frequency (HF) cards operate at 13.56 MHz — these are the newer MIFARE cards used in modern systems.

PrintedCards RFID cards use 13.56 MHz (MIFARE Classic standard). This is the dominant standard for new installations in India — most access control systems from ZKTeco, Hikvision, eSSL, Honeywell, and HID sold in India since 2015 support 13.56 MHz MIFARE. If your existing system uses 125 kHz EM cards (you can usually identify these by the plain white cards without any printing), contact us to confirm compatibility before ordering.

What Is NFC? How Is It Different from RFID?

NFC (Near Field Communication) is a subset of RFID operating at 13.56 MHz. All NFC is RFID, but not all RFID is NFC. The key difference is that NFC supports bidirectional communication — both the card and the reader can send and receive data — whereas standard RFID is typically one-way (card transmits UID, reader receives).

NFC is the technology used in tap-to-pay (Google Pay, PhonePe, credit cards) and in smartphone NFC. When a smartphone reads an NFC tag or card, it can interpret the data and take an action — opening a URL, saving a contact, or launching an app. This is what powers RFID visiting cards: the card contains an NFC chip programmed to open a URL when tapped with a phone.

Access control systems use RFID in the simpler sense — the card transmits its UID, the reader checks whether that UID is authorised, and unlocks the door or logs attendance. Visiting cards use NFC's ability to transmit a URL or contact record to any NFC-capable smartphone.

RFID ID Cards for Access Control and Attendance

For office door access, factory gates, laboratory entry, and school attendance, you need an RFID ID card that your existing reader can recognise. The reader stores a whitelist of authorised UIDs — one per enrolled card. When a card is tapped, the reader checks the UID against its database. If it matches an authorised entry, the door unlocks or the attendance is logged.

The card itself does not store any personal data on the chip — only the UID. All identity information (name, photo, designation) is printed on the card face and stored in your access control system's database, not on the chip.

NFC Visiting Cards — How They Work

An NFC visiting card is programmed with an NDEF record — a small data package that tells an NFC-capable phone what to do when it detects the card. Typically this is a URL record: when the phone reads the card, it opens the programmed URL in the browser. The URL might be your LinkedIn profile, a contact-sharing page (like Linktree or a vCard URL), your portfolio, or any web address.

No app is needed on the receiving phone — all modern NFC-enabled smartphones (iPhone 7+ and most Android phones since 2016) read NFC by default. The card owner's phone is not needed at all — only the other person's phone needs to do the reading.

At PrintedCards, RFID Visiting Cards can be pre-programmed with your URL before delivery. If you prefer to control the programming yourself (for example, to use a redirect URL you can update later without reprinting), we ship the cards blank and include instructions for programming with a free NFC-writing app.