Communications: electrical – Audible indication – Percussion-type sound producer
Patent
1975-10-09
1977-08-02
Sloyan, Thomas J.
Communications: electrical
Audible indication
Percussion-type sound producer
179 15AV, H03K 1324
Patent
active
040400492
ABSTRACT:
In a PCM system, character compression using nearly instantaneous companding (NIC) is known to obtain a reduction in the number of bits transmitted. Unfortunately, in tandem digital PCM-to-NIC-to-PCM conversions, a signal delay results because a maximum segment value is usually unknown until a block of PCM characters, which are to be converted to make up a block of NIC characters, has been received. Further, if the PCM block is received out-of-phase, a signal degradation may result because the incorrect maximum sgement value may be used during a subsequent conversion. To mitigate delay, the disclosed processor discards certain least significant bits of a PCM character and substitutes therefor a predetermined bit pattern corresponding to the difference between the maximum segment value and the segment value of the first character of the block. To mitigate degradation, the processor adjusts the block phase upon detection of the absence of a predetermined difference between the maximum segment value and the segment value of another character in the block.
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patent: 3778605 (1973-12-01), Montgomery
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Croll et al, "Nearly Instantaneous Digital Compandor -," Electronics Letters, vol. 9, No. 14, July 1973, pp. 298-300.
Croisier, "Progress in PCM and Delta Modulation: Block Companded-," International Zurich Seminar on Digital Communicatons, Mar. 1974, 4 pp.
Bell Telephone Laboratories Incorporated
Roddy Richard J.
Sloyan Thomas J.
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