Radio frequency identification (RFID) products use low, high, ultra-high and microwave frequencies to store, send, and retrieve data about monitored products or devices. There are several types of radio frequency identification (RFID) products. Tags or transponders are microchips that attach to RFID antennas and receive signals from and transmit signals to RFID readers. Each RFID tag contains a unique serial number and, in some cases, information such as a customer’s account number and location. RFID readers use radio waves to communicate with tags and send information in digital form to computerized systems. RFID antennas are conductive elements that enable tags to send and receive data. Transceivers are radio frequency identification (RFID) products that can both send and receive information. Special RFID printers are used to encode RFID tags. Complete RFID systems include tags, readers, and printers. 

Radio frequency identification (RFID) products use three basic technologies: active, passive, and semi-passive. Active RFID tags use a battery to power the microchip’s circuitry and transmit signals to readers. Typically, active tags can be read from distances of 100 ft. or more. Passive RFID tags do not include a battery. Instead, they draw power from a magnetic field that is formed by the coupling of the coiled antenna from a tag with the coiled antenna from a reader. Semi-passive tags are similar to active tags in that they use a battery to run the microchip’s circuitry; however, they do not communicate with RFID readers. To conserve battery life, some semi-passive tags remain in a “sleep” mode until contacted by a reader.   

Radio frequency identification (RFID) products differ in terms of performance specifications such as frequency range, memory, read rate, detection range, and operating temperature. Frequency range determines the applications for which RFID products are suitable. Memory determines the amount of data that tags or transponders can store. Measured in bits or bytes per second, read rate is the maximum rate at which data can be read from tags. Detection range is the distance at which readers can communicate with tags. With passive tags, the detection range is determined by the frequency, reader output, power, antenna design, and power-up method. 

Radio frequency identification (RFID) products provide many different communications interfaces. RS232 uses a serial binary data interchange and provides a standard interface between data terminal and data communications equipment. RS422 provides a balanced serial interface for the transmission of digital data and is designed for greater distances and higher baud rates. RS485, another common serial interface, can be transformed into a multi-point application. Inter-integrated circuit (I²C) is a relatively inexpensive, on-chip connection that allows devices to communicate with each other through a common bus. Universal serial bus (USB) is a 4-wire, 12-Mbps serial bus for low-to-medium speed peripheral device connections to personal computers (PC). Transistor-transistor logic (TTL) is a common type of digital circuit in which the output is derived from two transistors. Some radio frequency identification (RFID) products feature a wireless interface.

Selecting radio frequency identification (RFID) products requires an analysis of special features. Some radio frequency identification products include encryption to prevent unauthorized access to data. Others use anti-collision algorithms to prevent radio waves from one device from interfering with the radio waves from another. Portable RFID products are not attached to a fixed system. Non-contact devices do not require physical contact between readers and tags. Continuous reporting is a mode of reader operation in which a transponder ID is reported continuously while the transponder remains in the field of the reader.

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