# RFID 125 kHz Cards: A Comprehensive Guide ## What Are RFID 125 kHz Cards? **RFID 125 kHz cards** are low-frequency, passive radio-frequency identification cards operating at 125 kilohertz. These contactless cards are widely used for access control, time attendance, animal identification, and various security applications. I personally started using **RFID 125 kHz cards** over a decade ago when implementing a basic office access system, and I was impressed by their reliability and simplicity. ## Technical Specifications and Parameters When selecting **RFID 125 kHz cards**, understanding their technical specifications is crucial. Below are detailed parameters for a common chip type. ### EM4100-Compatible Card Specifications * **Operating Frequency:** 125 kHz ± 7 kHz * **Chip Code:** EM4100, EM4102, or compatible (e.g., T5557, EM4200 for read/write variants) * **Communication Protocol:** ASK (Amplitude Shift Keying) / Manchester Encoding * **Data Capacity:** 64 bits (typically 40 bits of unique ID + parity) * **Read Range:** 5 cm to 15 cm, depending on the reader's power * **Memory Type:** Read-Only (RO) or Read/Write (RW) depending on the chip * **Standard Dimensions (ISO/IEC 7810 ID-1):** * **Thickness:** 0.76 mm - 0.84 mm * **Width:** 85.60 mm * **Height:** 53.98 mm * **Corner Radius:** 2.88 mm - 3.48 mm * **Material:** PVC, ABS, or PET * **Operating Temperature:** -20°C to +70°C * **Data Retention:** >10 years * **Write Endurance:** 100,000 cycles (for RW chips) > **Important Note:** The technical parameters above are for reference data. Specific chip codes, exact dimensions, and performance metrics can vary by manufacturer and card model. For precise specifications for your project, please contact our backend management team. ## My Experience and Skill Development with RFID My journey with **RFID 125 kHz cards** began out of necessity for a small business security project. I discovered a natural aptitude for integrating hardware and simple software systems. This skill allowed me to design a custom door entry system that logged entries to a local database—a project that combined my interest in electronics with practical problem-solving. ## Opinion on the Current State of 125 kHz RFID Technology In my view, **RFID 125 kHz cards** remain incredibly relevant despite the rise of higher-frequency technologies like 13.56 MHz (HF) and UHF. Their primary strength lies in robustness and cost-effectiveness for short-range, single-purpose applications. Th