Catalog > Internet of Things (IOT) Related Products > More Platforms EM4100 125KHZ RFID Key Tags 125KHZ RFID Key Tags Key Tags EM4100 CMU RFID KEY 125KHZ EM4100 125KHZ RFID KEY TAG Discontinued Specifications, Prices & Availability may change without notice. Images are for illustration purposes only. E&OE Overview 125Khz Door Keeper keys, EM4100 Standard protocol, only read, can not write. Available in random colors. Use it together with 125Khz EM4100 RFID Card Read Module RDM630 UART Output Arduino shield.