An RC4Magic Series 3 or RC4Magic-900 DMXio transceiver can operate as either a transmitter or a receiver.  These modes can be manually selected, but the default is Auto Mode.  In this mode, the device automatically determines which mode it should be in.  Connect DMX data to a DMXio and it will be a transmitter.  Any other DMXio will find the transmitted signal and become a receiver.  This works because RC4Magic devices use private system IDs, ensuring that your receivers can never detect or act on signals from other systems.