A set of proprietary (Motorola) protocols for radio paging systems, FLEX largely has replaced POCSAG in the United States, and has become the de facto standard throughout most of the world, excepting Western Europe, where the ERMES standard is favored. FLEX solutions support duplex messaging and data transmission. FLEX supports as many as 5 billion addresses, with up to 600,000 supported per channel.The FLEX family of protocols includes the following: