Review on HiLetgo RDM6300 125kHz EM4100 RFID Card Read Module with UART Serial Output for Arduino by Missy Cooper

I bought this to test the ability to read multiple tags simultaneously within range of the antenna. Failed the test. It may be possible to read multiple tags without special built-in random delay hardware, but this reader cannot. Otherwise it worked perfectly when first plugged in. The output data has a serial speed of 9600 baud. The 0x02 byte follows the ASCII digit string, followed by 0x03 to end the string. If you keep the label within reach, only the ID will be retransmitted. This particular antenna has a very narrow range of distances over which it will be read. Most often it was 3cm. The antenna itself is a simple coil of wire, but the insulated wires attached to it have no strain relief, so handle them carefully or they will break.