Abstract: An asynchronous, addressable multiplex system comprises a master station in parallel communication with a number of slave stations. Both the master and slave stations employ independently clocked UAR/T's (universal asynchronous receiver/transmitter) circuits for simultaneous data receiving and transmitting, the UAR/T's communicating directly with one another. The master station includes means for formatting data to be transmitted by its UAR/T into message blocks each several bytes long and intended for a particular slave station whose address is encoded only in the first byte of the block. The message blocks are transmitted separated from one another by gaps which are two bytes long. Each slave station receives all master station message blocks and has means for recognizing the gaps and for then comparing the address in the first byte thereafter with an assigned slave station address. If the addresses correspond, the entire message block is accepted by the slave station.