Synchronization apparatus for a time division switching system

Claim 2

A time division switching system comprising a plurality of incoming lines, each line serving to carry digital data signals in time division multiplexed channels, a pair of receive data stores for each line, means for alternately writing the successive frames of data on a line into said pair of data stores, means for alternately reading out the data from each store in a manner such that the read out from one store generally occurs simultaneously with the write in to the other, control means for comparing the read and write store cycles for each line and for producing a control signal when the read and write cycles drift to a predetermined extent relative to each other, and means for coupling said control signal to the store read out means to cause the same to skip a frame of stored data or double-read a frame depending upon the relative direction of said drift.

Claim 3

A time division switching system as defined in claim 1 wherein said control means serves to generate a control signal when the read store cycle advances more than three-fourths into the write store cycle.

Claim 4

A time division switching system as defined in claim 2 including means for providing a circuit hysteresis effect for preventing repeated successive generation of the control signals during periods in which delay perturbations and jitter are sustained on a transmission line.

Claim 5

A time division switching system as defined in claim 3 including means for reading the data stores of a predetermined number of lines in succession so as to multiplex frames of data of said predetermined number of lines on to a multiplex bus.

Claim 6

A time division switching system as defined in claim 4 including means for adding parity check bits when appropriate to each of the multiplexed channels prior to the storage thereof.

Claim 7

A time division switching system as defined in claim 5 wherein said predetermined number is five.

Claim 8

In a stored-program-controlled time division switching machine, a plurality of incoming transmission lines, each transmission line serving to carry digital data signals in a predetermined number of time division multiplexed channels, a first and second receive data store for each line, means for alternately writing the successive frames of data on a transmission line into said first and second receive data stores, means for alternately reading out the data from said first and second stores a frame at a time and in a manner such that the read out from one store generally occurs simultaneously with the write into the other, a control means for each of said first and second receive data stores of each line, each control means serving to phase compare the read waveform of said first receive data store with the write waveform of said first receive data store for producing a first control signal when said read waveform effectively advances to a preselected extent in a given direction into said write waveform and for producing a second control signal when said read waveform effectively advances to a preselected extent in the opposite direction into said write waveform, and means for coupling said first and second control signals to the store read out means to cause the same to skip a frame of stored data when said first control signal is produced and to double-read a frame of stored data when said second control signal is produced, the relative direction of drift between said read and write waveforms being determinative of whether a frame of stored data is deleted or double-read.

Claim 9

In a stored-program-controlled time division switching machine, a plurality of incoming transmission lines, each transmission line serving to carry digital data signals in a predetermined number of time division multiplexed channels, a first and second receive data store for each line, means for alternately writing the successive frames of data on a transmission line into said first and second receive data stores, means for alternately reading out the data from said first and second stores a frame at a time and in a manner such that the read out from one store generally occurs simultaneously with the write into the other, a control means for each of said first and second receive data stores of each line, each control means serving to phase compare the read waveform of said first receive data store with the write waveform of said first receive data store for producing a first control signal when said read waveform effectively advances to a preselected extent in a given direction into said write waveform and for producing a second control signal when said read waveform effectively advances to a preselected extent in the opposite direction into said write waveform, and means for coupling said first and second control signals to the store read out means to cause the same to skip a frame of stored data when said first control signal is produced and to double-read a frame of stored data when said second control signal is produced, the relative direction of drift between said read and write waveforms being determinative of whether a frame of stored data is deleted or double-read.

Claim 10

A stored-program-controlled time division switching machine as defined in claim 7 including a means associated with each control means for providing a circuit hysteresis effect for preventing a rapid successive generation of first and second control signals during periods in which delay variations and jitter are encountered on a transmission line.