Error detection in multilevel transmission

Claim 2

In a pulse transmission system wherein pulses are transmitted in a partial response format characterized by multiple levels of pulse amplitude and a pulse correlation constraint of the form Bn AA- An x where Bn is the nth transmitted pulse, An is the nth signal pulse prior to correlation and An x is the (n-x)th pulse prior to correlation where x is an integer greater than one, means for monitoring the transmission for errors comprising means for sequentially maintaining a plurality of running sums of the different sets of related pulses defined by the constraint in the transmitted sequence, means for sequentially detecting violations of a code constraint in the running sums and for producing an output signal when a violation occurs, means responsive to the output signal for correcting the particular running sum in which the violation occurs, and means for delaying the running sum and feeding it back to said summing means in synchronism with the introduction of the next pulse of the set to be added to that particular running sum.

Claim 3

The transmission error monitoring system as claimed in claim 1 wherein the violation detecting means comprises means responsive to sums greater or less than the upper and lower limits respectively of a range of values less than the total range of the multiple pulse levels.

Claim 4

Apparatus for detecting errors in transmission of a multiple level pulse code of the partial response correlations type in which there are sets of related pulses comprising means for converting multilevel pulses to binary form, a first adder circuit connected to the converter output, and error monitor circuit connected to the output of said first adder for producing an output signal when the adder output exceeds a predetermined range of values, a pulse storage circuit to which the output of said monitor circuit is connected, an error correction signal generator circuit connected to the output of said pulse storage circuit, a second adder circuit into which the output of the first adder is fed after a delay and to which the output of the correction signal generator circuit is connected to produce a corrected sum at the output of said second adder, and means for feeding the output of said second adder back to saId first adder in synchronism with the application of the binary word representative of the next pulse in the particular set of which the output of the adder represents the running sum.

Claim 5

Apparatus for detecting errors in transmission of a multiple level pulse code of the partial response correlations type in which there are sets of related pulses comprising means for converting multilevel pulses to binary form, a first adder circuit connected to the converter output, and error monitor circuit connected to the output of said first adder for producing an output signal when the adder output exceeds a predetermined range of values, a pulse storage circuit to which the output of said monitor circuit is connected, an error correction signal generator circuit connected to the output of said pulse storage circuit, a second adder circuit into which the output of the first adder is fed after a delay and to which the output of the correction signal generator circuit is connected to produce a corrected sum at the output of said second adder, and means for feeding the output of said second adder back to saId first adder in synchronism with the application of the binary word representative of the next pulse in the particular set of which the output of the adder represents the running sum.

Claim 6

Apparatus as defined in claim 3 and further including a storage circuit between said first and second adder circuits, one output of said storage circuit being connected to said correction signal generator to control the sign of the correction signal.

Claim 7

Apparatus as claimed in claim 3 wherein said error monitor circuit comprises an exclusive OR gate.

Claim 8

Apparatus for detecting errors in transmission of a multilevel pulse code of the partial response correlation type in which time spaced nonadjacent pulses are related to each other, thereby defining sets of related pulses, comprising means for converting multilevel transmitted pulses into binary word form and applying each word in parallel form to a first adder, means connected to the first and second digit leads of the parallel output of said adder, said means being responsive to a difference in signal on said output leads to produce an error signal, means for storing said error signal and signal storage means for storing the output of said first adder, a correction signal generator circuit connected to the output of the error signal storing means and to one lead of the parallel output of said signal storing means, means for causing said signal storage means to release the word stored therein to a second adder and for causing said error-signal-storing means to release its stored signal to said correction signal generator, the output of said correction signal generator being connected to said second adder whereby the sum in said adder is corrected, and means connected to the output of said second adder for storing the output thereof until the next related pulse of the set is introduced into said first adder, and feeding back the stored output to said first adder in synchronism with the related pulse.

Claim 9

Apparatus for detecting errors in transmission of a multilevel pulse code of the partial response correlation type in which time spaced nonadjacent pulses are related to each other, thereby defining sets of related pulses, comprising means for converting multilevel transmitted pulses into binary word form and applying each word in parallel form to a first adder, means connected to the first and second digit leads of the parallel output of said adder, said means being responsive to a difference in signal on said output leads to produce an error signal, means for storing said error signal and signal storage means for storing the output of said first adder, a correction signal generator circuit connected to the output of the error signal storing means and to one lead of the parallel output of said signal storing means, means for causing said signal storage means to release the word stored therein to a second adder and for causing said error-signal-storing means to release its stored signal to said correction signal generator, the output of said correction signal generator being connected to said second adder whereby the sum in said adder is corrected, and means connected to the output of said second adder for storing the output thereof until the next related pulse of the set is introduced into said first adder, and feeding back the stored output to said first adder in synchronism with the related pulse.