Method of and system for handling conference calls in digital te

Details Method of and system for handling conference calls in digital te Method of and system for handling conference calls in digital te

1976-08-02

1978-02-28

Claffy, Kathleen H.

179 15AT, 179 15BW, H04M 356

Patent

active

040769666

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.

REFERENCES:
patent: 3755808 (1973-08-01), Candiani
patent: 3789392 (1974-01-01), Candiani
patent: 3984643 (1976-10-01), Inrig

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