This Recommendation deals with the setting up, lining up and characteristics of international data transmission systems operating at speeds in the range 2.4 to 14.4 kbit/s.The system may be a single connection operating at 2.4, 4.8,7.2, 9.6 or 14.4 kbit/s, or a combination of the lower speed systems, multiplexed onto the 9.6 or 14.4 kbit/s system.