Abstract: A plurality of digital signals of one or more digital transmission bit rates are arranged to be combined by employing a unique common channel frame format. The channel frame format includes a plurality of data bit positions and a plurality of overhead bit positions. The number of data bit positions used is dependent on the particular incoming signal. Similarly, the number of frames generated during a specific common framing interval is dependent on the digital transmission bit rate of the particular signal. Specifically, the number of channel frames generated during the common channel frame interval is dependent on a number of equivalent so-called lowest transmission bit rate signals included in the particular signal being formatted. The overhead bits are distributed in the channel frame format.

Abstract: In a transmission system, adding and/or dropping any one or more of a plurality of digital signals of one or more digital transmission bit rates is facilitated by employing a unique transmission signal in which data words associated with individual digital signals are arranged in prescribed groups. The transmission signal data word groups are obtained by formatting the individual digital signals to be combined into a unique channel frame format common to all of the digital signals and by employing a unique one-step multiplexing process to insert digital words from the channel frames into the group of data word positions in the transmission signal associated with the particular signal being combined. Consequently, digital signals may be added to the transmission signal by formatting them into the common channel frame format and, then, inserting the digital words therefrom in the one-step multiplexing process into an associated group of data words positions in the transmission signal.