Method of and system for handling conference calls in digital telephone exchange
First Claim
1. A method of linearly superposing significant portions of logarithmically coded coincident voice samples in a conference call, each voice-sample code consisting of a polarity bit, a plurality of higher-order range bits and a plurality of lower-order quantum bits, the numerical weights of said quantum bits depending on the rank of the code as determined by said range bits, comprising the steps of:
- a. separately storing a higher-ranking code and a lower-ranking code derived from a pair of coincident voice samples to be arithmetically combined;
b. downshifting the quantum bits of the lower-ranking code to less significant bit positions in which they would have their original numerical weights if prefaced by the range bits of the higher-ranking code;
c. comparing the polarity bits of the two codes stored in step (a); and
d. subjecting the quantum bits of the higher-ranking code and the downshifted quantum bits of the lower-ranking code to an algebraic summing operation with a sign depending on the relative values of the corresponding polarity bits as determined by step (c).
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Accused Products
Abstract
A telephone exchange linked via PCM channels with subscribers engaged in a conference call includes switching circuits for transmitting to each participating subscriber, during an assigned time slot, the albegraic sum of the digitized voice-current samples from all the other participants. The digitized samples are logarithmically coded, each code consisting of a polarity bit, three range bits and four quantum bits; in order to facilitate correct addition or subtraction of the quantum bits of two codes to be summed (unless these codes signify the two lowest-ranking ranges), according to whether their sign bits are identical or different, the quantum bits of a lower-ranking code are shifted in a register toward less significant bit positions in which they would have their original numerical weight when prefaced by the range bits of the higher-ranking code. The range bits are not summed but only those of the higher-ranking code are preserved, their numerical value being incremented by one in the case of addition but left unchanged or decremented by one (if a negative carry is present) in the case of subtraction. If the difference in rank exceeds the number of quantum bits, i.e. four, the lower-ranking code is ignored.
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Citations
12 Claims
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1. A method of linearly superposing significant portions of logarithmically coded coincident voice samples in a conference call, each voice-sample code consisting of a polarity bit, a plurality of higher-order range bits and a plurality of lower-order quantum bits, the numerical weights of said quantum bits depending on the rank of the code as determined by said range bits, comprising the steps of:
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a. separately storing a higher-ranking code and a lower-ranking code derived from a pair of coincident voice samples to be arithmetically combined; b. downshifting the quantum bits of the lower-ranking code to less significant bit positions in which they would have their original numerical weights if prefaced by the range bits of the higher-ranking code; c. comparing the polarity bits of the two codes stored in step (a); and d. subjecting the quantum bits of the higher-ranking code and the downshifted quantum bits of the lower-ranking code to an algebraic summing operation with a sign depending on the relative values of the corresponding polarity bits as determined by step (c). - View Dependent Claims (2, 3, 4)
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5. A system for linearly superposing significant portions of logarithmically coded voice samples in a conference call, each voice-sample code consisting of a polarity bit, a plurality of higher-order range bits and a plurality of lower-order quantum bits, the numerical weights of said quantum bits depending on the rank of the code as determined by said range bits, comprising:
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code-receiving means including two storage circuits each including first register means for storing polarity and range bits and second register means for storing quantum bits of respective codes to be arithmetically combined; first arithmetic means connected to said first register means for determining the difference in ranks between said respective codes; linearization means connected to said second register means and controlled by said first arithmetic means for downshifting the quantum bits of the lower-ranking code to less significant bit positions in which they would have their original numerical weights if prefaced by the range bits of the higher-ranking code; second arithmetic means connected to said second register means and controlled by the contents of said first register means for subjecting the quantum bits of the higher-ranking code and the downshifted quantum bits of the lower-ranking code to an algebraic summing operation with a sign depending on the relative values of the corresponding polarity bits; and evaluation means connected to said first and second arithmetic means for deriving a composite code from the range bits of the higher-ranking code and the quantum bits resulting from said algebraic summing operation. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12)
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Specification