Data rate conversion and supervisory bit insertion in a data system
AssigneeGTE Communications Products Corporation
InventorsJohn B. McNesby, Joseph F. Krys
Life of this patent
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Abstract
A data rate converter for use in telecommunications inserts supervisory bits into a data stream to increase the data rate, in one application, from 56 kbps to a standard 64 kbps. A standard 64 kbps PCM telephone channel uses 8-bit words for transmission, whereas 56 kbps occupies only 7 bits of an 8 bit word in such a telephone channel. Supervisory bits are inserted at the exact time when the data channel clock signal and the transmission line clock signal are in phase alignment.
Claims6
Digital transmission apparatus adapted to accept binary data from a data source and to convert said data into a serial pulse train formed of words having n bits per byte in n equal-length time slots at a line transmission rate L, and wherein said binary data has a bit rate M which is less than said line transmission rate L, said apparatus comprising:
- timing means generating a first clock signal of bit rate L and a second clock signal of bit rate M;
- synchronizing means, responsive to said second clock signal and to said binary data, providing a synchronized binary data signal in phase with said second clock signal of bit rate M;
- retiming means, responsive to said first clock signal and to said synchronized binary data signal, providing a retimed binary data signal of bit rate M;
- comparison means, responsive to said first and second clock signals, providing a coincidence output signal when said first and second clock signals are in phase alignment;
- and
- multiplexing means for increasing the bit rate of said retimed binary data signal from M to L and for inserting additional bits into said retimed binary data signal at appropriate time slots in response to said coincidence output signal, and thereby providing a serial pulse train at the desired line transmission rate L.
Dependencies are inferred from the claim text.