System for transporting full T1 frame of data/voice channels and additional DSO data channels over E1 communication link

In addition using twenty-four DS0 channels of an E1 transport rate-based digital communication link to convey an entire T1 frame of voice/data channels, an additional 364 Kbps bandwidth is used to convey a plurality of (up to six) DS0 data channels, without having to modify the signaling properties of the T1 frame into the higher transport rate protocol. For non-primary T1 voice channels, robbed encoded signaling bits are inserted 'as is' into the E1 signaling channel and mu-law encoded voice is inserted into 24 DS0 channels of the E1 frame. For primary rate ISDN (having no robbed bits), the signaling channel of the E1 frame becomes available for any ISDN channel. This allows the 'D' channel of the ISDN frame to be inserted in any of the thirty-one available E1 time slots.