Transparent technique for Mu-law modems to detect an all-digital circuit connection
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United States of America Patent
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Jun 27, 2000
Grant Date -
N/A
app pub date -
Aug 15, 1997
filing date -
Aug 15, 1997
priority date (Note) -
Expired
status (Latency Note)
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Abstract
A transmitting Mu-law modem creates a probe signal by modifying the 7th bit of each of a number of PCM samples during the 'hand-shaking' phase of a data connection. Furthermore, the transmitting Mu-law modem only makes this modification on those PCM samples that fall into the range of segment 1 as defined in CCITT Recommendation G.711. Similarly, a receiving Mu-law modem searches for this known pattern. Upon detection of this pattern, the receiving Mu-law modem provides an acknowledgment signal and both modems subsequently switch to a digital-mode of operation. On the other hand, if, in fact, there is a least one analog link in the data connection, the probe signal becomes distorted and, since the receiving Mu-law modem does not detect the probe signal, handshaking is completed in the standard fashion.
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