This Recommendation defines the general principles and parameters of the muldex that is used to send telegraph signals and low-speed data using TDM bit-interleaving with an aggregate bit rate higher than 4800 bit/s on an analogue telephone-type circuit or a higher order TDM system. In this Recommendation telegraph TDM systems are used for framing, and therefore there is no need to standardize a special frame structure for the aggregate bit rates higher than 4800 bit/s.