Digital frame synchronizer
First Claim
1. A synchronizer in which digital signals at a first transmission bit rate are synchronized by use of bit stuffing to a second higher transmission bit rate for transmission in an output frame format, comprising,means for obtaining a predetermined fractional stuffing ratio for output frames from said synchronizer, said means for obtaining including means for controllably varying in a prescribed manner intervals during which data bits are being inputted into said synchronizer, wherein a fractional stuffing ratio is obtained.
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Abstract
A desired positive fractional stuffing ratio is obtained in a frame synchronizer for a digital signal having a channel frame format that included two stuffing bit positions to obtain either positive or negative stuffing. The fractional stuffing ratio is obtained by controllably increasing the duration of a first predetermined number of intervals during which data bits are written into the synchronizer and, then, by controllably decreasing the duration of a second predetermined number of intervals during which data bits are written into the synchronizer. A data bit is forced to be included in one of the stuffing bit positions occurring during each of the first predetermined number of intervals and a non-data bit is forced to be included in one of the stuffing bit positions occurring during each of the second predetermined number of intervals.
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Citations
20 Claims
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1. A synchronizer in which digital signals at a first transmission bit rate are synchronized by use of bit stuffing to a second higher transmission bit rate for transmission in an output frame format, comprising,
means for obtaining a predetermined fractional stuffing ratio for output frames from said synchronizer, said means for obtaining including means for controllably varying in a prescribed manner intervals during which data bits are being inputted into said synchronizer, wherein a fractional stuffing ratio is obtained.
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9. A synchronizer in which digital signals at a first transmission bit rate are synchronized by use of bit stuffing to a second higher transmission bit rate for transmission in an output frame format, comprising,
an asynchronous stuffing stage for generating intermediate frames, means associated with said asynchronous stuffing stage for controllably increasing the nominal number of incoming data bits accommodated for a first predetermined number of said intermediate frames and for controllably decreasing the nominal number of incoming data bits accommodated for a second predetermined number of said intermediate frames, and a synchronous stuffing stage supplied with said intermediate frames for generating output frames each having a predetermined number of bits, wherein a fractional stuffing ratio is obtained.
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14. A synchronizer in which digital signals at a first transmission bit rate are synchronized by use of bit stuffing to a second higher transmission bit rate for transmission in an output frame format, comprising,
an elastic store, means for controlling writing incoming data bits into said elastic store, means for controlling reading data bits out of said elastic store, and means for controlling stuffing of bits into stuffing bit positions, said means for controlling writing including means for controllably increasing the duration of a first predetermined number of intervals during which data bits are written into said elastic store and for controllably decreasing the duration of a second predetermined number of intervals during which data bits are written into said elastic store, wherein a fractional stuffing ratio is obtained.
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19. A method of synchronizing digital signals at a first transmission bit rate by use of bit stuffing to a second higher transmission bit rate for transmission in an output frame format, comprising the steps of,
increasing the duration of a first predetermined number of intervals during which incoming data bits are written into a bit stuffing synchronizer, and decreasing the duration of a second predetermined number of intervals during which incoming data bits are written into said bit stuffing synchronizer, wherein a fractional stuffing ratio is obtained.
Specification