The Radio Frequency Identification (RFID) Read/Write Module provides a low-cost solution to read and write passive RFID transponder tags up to 4 inches away.

The RFID Read/Write module can be used in a wide variety of hobbyist and commercial applications, including access control, user identification, robotics navigation, inventory tracking, payment systems, car immobilization, and manufacturing automation.

The module works exclusively with the EM Microelectronic-Marin SA EM4x50 1kbit R/W transponder tags. Each tag contains a unique, read-only serial number (one of 2 ³² , or 4,294,967,296 possible combinations) and 116 bytes of user data area stored in a non-volatile EEPROM (Electrically Erasable Read Only Memory). The user data area can be optionally secured with a 32-bit password to allow only authorized read and write operations.

Parallax, Inc. was the exclusive manufacturer of the RFID Read/Write module. The USB version has been discontinued as of December 6, 2021. The Serial (2-wire, 9600 baud, TTL-level) version has been discontinued as of September 19, 2023.