Access control card readers are mainly divided into 125 kHz (low frequency),13.56 MHz (high frequency) as well as 915 MHz (Ultra-high frequency) Three frequencies, each corresponding to different security and low-voltage engineering application scenarios.

125 kHz low frequency (ID card)
Features: Mature technology, low cost, commonly known as "ID card" or "proximity card".
Advantages: Strong penetration (can penetrate water and has good metal sensing ability), and relatively long reading distance.
Disadvantages: Extremely low security. The card only contains a fixed ID number with no encryption protection, and can be easily copied using a device costing a few hundred yuan.
Suitable for: Access control systems in general offices or older apartments with limited budgets and low security requirements.
13.56 MHz High Frequency (IC Card/NFC)
Features: It is currently the mainstream standard for access control, also known as "IC card" or "Mifare card", and is compatible with NFC technology.
Advantages: High security. Supports encrypted operations and multi-block storage, making it difficult to copy. Supports EasyCard, iPass, or mobile NFC as access control credentials.
Disadvantages: The sensing distance is relatively short (usually within 10 cm), and it is more susceptible to interference from metal shielding.
Applicable scenarios: modern residential buildings, corporate headquarters, government agencies, or systems that require integrated card systems.
915 MHz Ultra-High Frequency (UHF)
Features: Long-range sensing technology, using the same frequency band as RFID used for logistics tracking.
Advantages: Long sensing distance (up to several meters), no need to get out of the car or get close to the card reader to identify the card.
Disadvantages: It is highly directional and easily affected by the environment, rain, or window tinting.
Applicable scenarios: license plate recognition assistance in parking lots, automatic gates, and material access control in large factories.

To quickly determine the frequency of an access control card reader, the fastest method on-site is to "check the external markings + check the card type + test with a mobile phone/NFC + and if necessary, use a frequency tester".

First, check the card reader or card label.
Most intuitive:

125kHzCommon writing styles include
EM,EM ID,Proximity,125KHz
13.56MHzCommon writing styles include
Mifare,IC,NFC,13.56MHz,DESFire

II. Consider the card thickness and its intended use.
Coarse classification and quick judgment:

125kHz ID card
- Mostly just card number recognition
- Common types include "thick cards, thin cards, and keychains".
- generallyCannot store value, cannot write data to partitions
- Many older access control systems use this type of technology.
13.56MHz IC card
- Commonly found in Mifare and NFC systems
- Partition encryption and data storage are supported.
- Commonly integrated access control, attendance, elevator, and payment systems
- New sales sites and smart buildings are more common.

III. Fastest test using a mobile phone
This is very useful:

if 13.56MHz (NFC/Mifare class)
- Enable NFC on Android phones
- When a card is close to a phone, it often has a chance of being detected.
If mobile phoneNo response at all
- It is very likely 125kHz
- Because mobile phone NFC almost never supports 125kHz.

Notice:

Not all 13.56MHz cards can be fully read by mobile phones.
butThe phone has a sensorMost of them can be initially determined to belong to the 13.56MHz class.

Fourth, observing the card reading distance can also provide a rough judgment.

125kHz:
- The typical sensing distance is usually short to medium.
- Mostly simple card swipe to open the door
13.56MHz:
- Most of them are also close-range.
- However, it has strong data interaction capabilities.

soRelying solely on distance is inaccurateIt can only assist in the judgment.

V. Most accurate and fastest: using a frequency test card/card reader.
Commonly used on-site in low-voltage electrical engineering:

Access control frequency tester
RFID Reader Tester
Dual-frequency test card

You can tell it's there as soon as you stick it on:

125kHz
13.56MHz
or dual-frequency

VI. Quick Judgment Tips for Dismantling Low-Voltage Electrical Engineering Projects
You can remember it like this:

Seeing EM, ID, and Proximity → I'd guess 125kHz first.
Seeing Mifare, IC, and NFC → I'll guess 13.56MHz first → EasyCard can be used
The phone's NFC can read the signal → It can almost determine 13.56MHz.
The phone can't read it at all, and it's an old access control system → most likely 125kHz.

VII. Supplement: Some are dual-band or have special specifications.
Some access control systems now support more than one frequency and may support:

125kHz + 13.56MHz
CPU card
DESFire
FeliCa
UHF Special Applications

So if you are going to doReplacement, integration, repair or low-voltage system inventory,

Experience sharing from the Low Voltage Engineering Department

When you bring a credit card with EasyCard functionality close to the access control card reader, it will make a sound.

This means it is 13.56MHz.

Since the EasyCard is classified as a payment card type at 13.56MHz, the following is a summary of the advantages and disadvantages of 125kHz and 13.56MHz.

Key Differences Summary:

Feature	125 kHz (LF)	13.56 MHz (HF)
Security	Low (easy to clone)	High (encrypted)
Data Speed	Slow	Fast
Range	Very Short (1-5 cm)	Short (up to 1m)
Metal Tolerance	High	Moderate/Low
Best For	Basic Access	Payments/Secure Access

However, FGT's low-voltage engineering department suggests...

Don't rely solely on appearance; it's best to:

Read product model
Check catalog
Confirm with a tester

The following is

The Taiwan access control card reader market is dominated by local brands, which offer mature technology and comprehensive after-sales service. Below are some of the most common Taiwanese brands on the market:

Leading brand (high market share and brand awareness)
SOYAL (Maoxu Information)A leading brand with a very high market share in Taiwan, offering a wide range of products, from home standalone models to commercial networked models. Its 721/725 series are standard equipment in many communities and office buildings.
HUNDURE (Hanjun Technology)Established access control manufacturers excel in customized solutions and high integration, such as the "dual card matching" commonly used in the financial industry or the "multi-door interlocking" function used by technology companies.
Pegasus (鹏骥产业)Pegasus is a global brand specializing in RFID card readers, sensor main units, and time and attendance systems, offering a variety of cardless or dual-frequency solutions.
Professional security and electronic lock brand
WAFERLOCKA well-known Taiwanese electronic lock manufacturer specializing in smart home and hotel access control, with strengths in electronic door handle locks and cloud management platforms.
SOCA (Xuan Guan)Specializing in various electronic locks (magnetic locks, anode locks) and access control controllers, often used in conjunction with other system manufacturers.
WIT (Webo System)They offer card readers with a strong sense of design, such as touch screen and metal casing, and also focus on parking management and elevator floor control.
Other common brands
DJS (E-Tech)It has a high reputation in the security monitoring industry and provides multi-functional access control hosts that combine facial recognition, fingerprint and QR code.
Heart Tech (联忠科技)Provides a stable access management system for industrial and commercial environments.