Technology of Punch Time Clocks: RFID Nov 04, 2019

RFID is a non-contact automatic identification technology. In short, it is to identify the target object and obtain relevant data through radio frequency. The identification work does not need human intervention. As the wireless version of barcode, RFID technology has the advantages of waterproof, antimagnetic, heat-resistant, long service life, large reading distance, data encryption on label, larger storage capacity, and free change of storage information that barcode does not have. It will bring revolutionary changes to retail, material flow and other industries. As a kind of communication technology, it can identify specific target and read and write relevant data through wireless signal. This technology is used in punch time clocks today.


RFID can be divided into low frequency, high frequency, ultra-high frequency and microwave according to different application frequencies. The corresponding representative frequencies are: low frequency below 135KHz, high frequency 13.56MHz, ultra-high frequency 860m ~ 960MHz and microwave 2.4G, 5.8G.

RFID is divided into passive RFID, active RFID and semi-active RFID according to the way of energy supply. Passive RFID has a short read-write distance and low price; active RFID can provide a longer read-write distance. It has a higher cost and is suitable for long-distance reading and writing applications.

Principle introduction

The principle of RFID technology is not complicated: after the tag enters the magnetic field, it receives the signal from the reader, sends the information by the inductive current, or actively sends the signal of a certain frequency. After reading and decoding the information, the interpreter will send it to the central information system for data processing.

According to the communication and energy sensing between RFID reader and tag, it can be divided into two types: inductive coupling and backscatter coupling. Generally, low-frequency RFID mostly adopts the first method, while high-frequency RFID mostly adopts the second method.

The reader can be read or read / write device according to the structure and technology used. It is the information control and processing center of RFID system. The information exchange between reader and transponder is usually carried out by half duplex communication.


Tag: it is composed of coupling elements and chips. Each tag has a unique electronic code and is attached to the object to identify the target object.

Reader: a device for reading label information, which can be designed as hand-held or fixed type.

Antenna: in the electronic tag of transmitting RF signal between tag and reader, the electronic data in the agreed format is generally saved, so as to achieve the purpose of automatic identification. The read tag information is transmitted to the computer for further processing.