Device for inserting information bits into a specific frame structure

Claim 1

A device for inserting information bits into a specific frame structure at specific locations at least one of which may contain at least one justification opportunity bit, said device comprising: means for dividing the incoming digital bit stream with bit rate D1 into N bit streams with a reduced bit rate D1/N, a buffer memory into which are written at the bit rate D1/N and read at the bit rate D2/N successive words of n bits from said dividing mean, where D2/N denotes a reduced insertion bit rate at which said words are inserted in the outgoing frames, associated with justification control means adapted to compare the read and write bit rates of said buffer memory and generate a justification command, an elastic memory having a capacity determined to contain at each time defined by the reduced insertion bit rate D2/N a variable number of bits of words read in said buffer memory and not yet inserted or not yet reinserted into the outgoing frames, said variable number varying according to previously generated justification commands, means for selecting at each time defined by the reduced insertion bit rate D2/N, and according to previously generated justification commands, n bits contained in said elastic memory which are to be inserted or are to be reinserted at this time, means for providing a signal representing a present value of said variable number, and means responsive to said signal for temporarily blocking the clock for reading said buffer memory if the justification command generated at a given time is such that the number of bits to be stored in said elastic memory exceeds a predetermined limit value.

Claim 2

A device for inserting information bits into a specific frame structure at specific locations at least one of which may contain at least one justification opportunity bit, said device comprising: means for dividing the incoming digital bit stream with bit rate D1 into N bit streams with a reduced bit rate D1/N, a buffer memory into which are written at the bit rate D1/N and read at the bit rate D2/N successive words of n bits from said dividing mean, where D2/N denotes a reduced insertion bit rate at which said words are inserted in the outgoing frames, associated with justification control means adapted to compare the read and write bit rates of said buffer memory and generate a justification command, an elastic memory having a capacity determined to contain at each time defined by the reduced insertion bit rate D2/N a variable number of bits of words read in said buffer memory and not yet inserted or not yet reinserted into the outgoing frames, said variable number varying according to previously generated justification commands, means for selecting at each time defined by the reduced insertion bit rate D2/N, and according to previously generated justification commands, n bits contained in said elastic memory which are to be inserted or are to be reinserted at this time, means for providing a signal representing a present value of said variable number, and means responsive to said signal for temporarily blocking the clock for reading said buffer memory if the justification command generated at a given time is such that the number of bits to be stored in said elastic memory exceeds a predetermined limit value.