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Claims  |
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I claim:
1. Apparatus for use at a receiver for receiving through telephone lines
from a transmitter analog signals corresponding to digital signals
representing data in accordance with a plurality of analog levels and
modulated in a first pseudo random code involving the analog levels, the
received signals including echoes of analog signals transmitted from the
receiver to the transmitter and reflected from the transmitter back to the
receiver and modulated in a second pseudo random code different from the
first pseudo random code, including,
first means at the receiver for converting the analog signals received in
the first and second pseudo random codes from the transmitter to digital
signals representing the analog signals,
second means at the receiver for providing digital signals modulated in the
second pseudo random code,
third means at the receiver, the third means being responsive to the
digital signals from the second means and to the digital signals from the
first means for eliminating from the digital signals from the first means
the modulated digital signals reflected in the second pseudo random code
from the transmitter back to the receiver,
the second means including an echo canceller having a plurality of
successive terminals and providing for a shift of the digital signals in
the second pseudo random code from the second means to the successive
terminals and having adjustable coefficients at the successive terminals
for adjusting the digital signals in the second pseudo random code the
third means including fourth means for comparing the digital signals from
the first means and the adjusted digital signals at the successive
terminals in the echo canceller to obtain digital signals representing the
results of such comparison and for adjusting the digital signals
representing the adjustable coefficients for the successive terminals in
the echo canceller in accordance with the results of such comparison, the
second means further including memory means for storing the adjusted
digital signals representing the adjustable coefficients at the successive
terminals in the echo canceller and for storing the digital signals from
the second means.
2. Apparatus as set forth in claim 1, including,
the fourth means operating upon the adjusted digital signals stored in the
memory means and representing the adjustable coefficients at the
successive terminals in the echo canceller and the digital signals stored
in the memory means from the second means and the digital signals from the
first means to obtain the adjusted digital signals representing the
adjustable coefficients at the successive terminals in the echo canceller.
3. Apparatus as set forth in claim 2, including,
the second means including fifth means for using the adjusted digital
signals representing the adjustable coefficients stored in the memory
means for the successive terminals in the echo canceller to obtain the
adjustments in the adjustable coefficients at such successive terminals in
an next introduction to the third means of the digital signals from the
first means.
4. Apparatus as set forth in claim 1, including,
sixth means for integrating the adjustments in the digital signals
representing the adjustable coefficients in the successive comparisons by
the fourth means to obtain the adjusted digital signals representing the
adjustable coefficients in the echo canceller for an introduction to the
fourth means in a next comparison by the fourth means.
5. Apparatus for use at a receiver for receiving through telephone lines
from a transmitter analog signals corresponding to digital signals
representing data in accordance with a plurality of analog levels and
modulated in a first pseudo random code involving the analog levels, the
received signals including echoes of analog signals transmitted from the
receiver to the transmitter and reflected from the transmitter back to the
receiver and modulated in a second pseudo random code different from the
first pseudo random code, including,
first means at the receiver for providing digital signals representing the
analog signals received in the first and second pseudo random codes from
the transmitter,
second means at the receiver for providing digital signals modulated in the
second pseudo random code,
third means at the receiver, and including a plurality of terminals each
providing adjustable digital signals representing an adjustable
coefficient, for adjusting the modulated digital signals from the second
means in accordance with such adjustable coefficients,
fourth means at the receiver for comparing the digital signals from the
first means and the signals from the plurality of terminals at the third
means and for producing digital signals in accordance with such comparison
to obtain adjustments in the adjustable coefficients at the third means,
fifth means responsive to the digital signals from the fourth means for
adjusting the digital signals representing the adjustable coefficients at
the terminals in the third means, and
memory means for storing the adjusted digital signals representing the
adjustable coefficients at the different terminals in the third means for
use by the fourth means in producing the digital signals providing for an
adjustment the adjustable coefficients at the third means.
6. Apparatus as set forth in claim 5, including,
sixth means for storing in the memory means the modulated digital signals
from the second means for adjustment of such modulated digital signals in
accordance with the adjusted digital signals representing the adjustable
coefficients stored in the memory means.
7. Apparatus as set forth in claim 5, including,
the fourth means providing digital signals substantially eliminating
reflections of the digital signals transmitted in the second pseudo random
code from the receiver to the transmitter and reflected by the transmitter
to the receiver, and
sixth means responsive at the receiver to the digital signals from the
fourth means for reproducing the data represented by the digital signals
transmitted in the first pseudo random code from the transmitter to the
receiver.
8. Apparatus as set forth in claim 5, including,
the echo canceller constituting a first echo canceller,
sixth means at the receiver, and including a second echo canceller having a
second plurality of terminals less than the first plurality with each of
the second terminals providing adjustable digital signals representing an
adjustable coefficient, for adjusting the digital signals from the fourth
means in accordance with such adjustable coefficients,
seventh means at the receiver for comparing the digital digital signals
from the fourth means and the signals from the second plurality of
terminals at the sixth means and for producing digital signals in
accordance with such comparison to obtain adjustments in the adjustable
coefficients at the terminals in the sixth means, and
eighth means responsive to the digital signals from the seventh means for
adjusting the digital signals representing the adjustable coefficients at
the terminals in the sixth means,
the memory means being operative to store the adjustable coefficients for
the different terminals in the sixth means for use in the comparison by
the seventh means.
9. Apparatus as set forth in claim 8, including,
ninth means for storing in the memory means the digital signals modulated
in the second pseudo random code from the second means for comparison with
the digital signals from the first means,
tenth means for storing in the memory means the digital signals modulated
in the second pseudo random code from the second means,
the seventh means providing digital signals in the first pseudo random code
and substantially eliminating any reflection of the digital signals
transmitted in the second pseudo random code from the receiver to the
transmitter and reflected by the transmitter to the receiver, and
eleventh means responsive at the receiver to the digital signals in the
first pseudo random code from the seventh means for reproducing the data
represented by such digital signals.
10. Apparatus for use at a receiver for receiving through telephone lines
from a transmitter analog signals corresponding to digital signals
representing data in accordance with a plurality of analog levels and
modulated in a first pseudo random code involving the analog levels, the
received signals including echoes of analog signals transmitted from the
receiver to the transmitter and reflected from the transmitter back to the
receiver and modulated in a second pseudo random code different from the
first pseudo random code, including,
first means at the receiver for providing digital signals representing the
analog signals received in the first and second pseudo random codes from
the transmitter,
second means at the receiver for providing digital signals modulated in the
second pseudo random code,
third means including an echo canceller for receiving from the second means
the digital signals modulated in the second pseudo random code, the third
means having a plurality of terminals each providing digital signals
representing an individual coefficient,
memory means for storing the digital signals representing the individual
coefficients at the different terminals in the third means,
fourth means for adjusting the modulated digital signals from the second
means in accordance with the digital signals stored in the memory means
for the individual coefficients at the different terminals in the third
means,
fifth means for comparing the digital signals in the first pseudo random
code from the first means and the adjusted modulated digital signals from
the fourth means and for producing signals representing the differences in
such comparison, and
sixth means responsive to the signals representing the differences in the
comparison from the fifth means and the digital signals from the memory
means in representation of the individual coefficients at the different
terminals in the third means for providing digital signals representing
adjusted values of the adjustable coefficients at the different terminals
in the third means and for storing such digital signals in the memory
means for introduction to the fifth means in the operation of the fifth
means in producing the digital signals representing the differences in the
comparison.
11. Apparatus as set forth in claim 10, including,
seventh means for storing in the memory means the digital signals modulated
in the second pseudo random code from the second means and for introducing
such stored signals to the fourth means for the adjustment of such
modulated digital signals in accordance with the digital signals stored in
the memory means for the individual coefficients at the different
terminals in the third means.
12. Apparatus as set forth in claim 10, including,
seventh means responsive to the digital signals representing the
differences from the fifth means for recovering the data represented by
the digital signals in the first pseudo random code from the first means.
13. Apparatus as set forth in claim 12, including,
the memory means being operative to store the digital signals modulated in
the second pseudo random code from the second means,
the sixth means including seventh means responsive to the digital signals
in the memory means in representation of the modulations in the second
pseudo random code and in representation of the adjustable coefficients at
the terminals in the echo canceller and responsive to the digital signals
representing the digital signals from the fifth means for providing,
the digital signals representing updated values of the individual
coefficients at the different terminals in the third means.
14. Apparatus for use at a receiver for receiving through telephone lines
from a transmitter analog signals corresponding to digital signals
representing data in accordance with a plurality of analog levels and
modulated in a first pseudo random code involving the analog levels, the
received signals including echoes of analog signals transmitted from the
receiver to the transmitter and reflected from the transmitter back to the
receiver and modulated in a second pseudo random pattern different from
the first pseudo random pattern, including,
first means for providing digital signals representing the analog signals
received in the first and second pseudo random codes from the transmitter,
second means at the receiver for providing digital signals modulated in the
second pseudo random code,
third means including an echo canceller for receiving the digital signals
modulated in the second pseudo random code from the second means, the
third means having a plurality of terminals each providing digital signals
representing an individual coefficient,
memory means for storing the digital signals modulated in the second pseudo
random code from the second means,
fourth means for adjusting the digital signals in the second pseudo random
code from the second means in accordance with the digital signals at the
terminals in the third means,
fifth means for combining the the digital signals from the fourth means and
the digital signals modulated in the first and second pseudo random codes
from the first means for producing digital signals representing updated
values of the coefficients at the different terminals in the third means,
sixth means for storing the digital signals from the fifth means in the
memory means, and
seventh means for combining the digital signals representing the updated
values of the coefficients in the memory means and the digital signals
modulated in the second pseudo random code from the memory means to
produce updated digital signals representing the coefficients at the
different terminals in the third means for introduction to the fourth
means for combination with the digital signals in the second pseudo random
code from the second means.
15. Apparatus as set forth in claim 14, including,
the echo canceller in the third means constituting a first echo canceller
having a first plurality of terminals each providing digital signals
representing an individual coefficient,
eighth means including a second echo canceller for receiving the digital
signals modulated in the second pseudo random code from the second means,
the eighth means having a second plurality of terminals, less than the
first plurality, each of the terminals in the eighth means providing
digital signals representing an individual coefficient,
ninth means for adjusting the digital signals modulated in the second
pseudo code from the second means in accordance with the digital signals
from the terminals in the eighth means, and
tenth means for combining the adjusted digital signals from the ninth means
and the digital signals from the fourth means to produce digital signals
representing updated values of the individual coefficients at the
different terminals in the eighth means, and
twelfth means for combining the digital signals from the tenth means and
the digital signals stored in the memory means from the second means to
produce digital signals representing
the ninth means being responsive to the digital signals stored in the
memory means from the tenth means and the digital signals modulated in the
second pseudo random code from the second means for providing adjustments
in the digital signals in the second pseudo random code from the second
means.
16. Apparatus as set forth in claim 15, including,
thirteenth means responsive to the digital signals from the ninth means for
operating upon such digital signals to provide digital signals
representing the data transmitted from the transmitter to the receiver.
17. Apparatus as set forth in claim 14, including,
eighth means for processing the signals from the fourth means to provide
digital signals representing the data transmitted from the transmitter to
the receiver.
18. Apparatus for use at a receiver for receiving through telephone lines
from a transmitter analog signals corresponding to digital signals
representing data in accordance with a plurality of analog levels and
modulated in a first pseudo random code involving the analog levels, the
received signals including echoes of analog signals transmitted from the
receiver to the transmitter and reflected from the transmitter back to the
receiver and modulated in a second pseudo random code different from the
first pseudo random code, including,
first means at the receiver for converting the analog signals received in
the first and second pseudo random code from the transmitter to digital
signals representing the analog signals,
second means at the receiver for providing digital signals modulated in the
second pseudo random code,
third means including an echo canceller for receiving the digital signals
in the second pseudo random code from the second means, the third means
having a plurality of terminals each providing digital signals
representing an individual coefficient, the third means being operative to
adjust the digital signals in the second pseudo random code from the
second means in accordance with the digital signals representing the
individual coefficients,
fourth means for processing the digital signals in the first and second
pseudo random codes from the first means and the adjusted digital signals
in the second pseudo random code from the third means to produce digital
signals representing differences in the values of the digital signals
being processed,
memory means for storing the digital signals in the second pseudo random
code from the second means upon each production of the digital signals in
the first and second pseudo random codes from the first means and for
storing digital signals representing the coefficients at the different
terminals in the third means, and
fifth means responsive to the digital signals representing the differences
from the fourth means and the stored digital signals representing the
coefficients at the different terminals in the third means and the digital
signals in the second pseudo random code from the second means for
producing digital signals representing updated values of the coefficients
at the different terminals in the third means and for storing such
produced digital signals in the memory means as the coefficients at the
different terminals in the third means.
19. Apparatus as set forth in claim 18, including,
the echo canceller constituting a first echo canceller,
sixth means including a second echo canceller for receiving the digital
signals in the second pseudo random code from the second means, the sixth
means having a plurality of terminals, less than the plurality of
terminals in the third means, each of the terminals in the sixth means
providing digital signals representing an individual coefficient, the
sixth means being operative to adjust the digital signals in the second
pseudo random code from the second means in accordance with the digital
signals representing the coefficients in the sixth means,
seventh means for processing the digital signals representing the
differences from the fourth means and the adjusted digital signals in the
second pseudo random code from the sixth means to produce digital signals
representing differences in the values of the digital signals being
processed,
the memory means for storing the digital signals in the second pseudo
random code from the second means upon each production of the digital
signals from the fourth means and for storing digital signals representing
the coefficients at the different terminals in the seventh means, and
eighth means responsive to the digital signals representing the differences
from the seventh means and to the digital signals representing the
coefficients from the second memory means and to the digital signals in
the second pseudo random code from the second means for producing digital
signals representing updated values of the coefficients at the different
terminals in the sixth means and for storing such produced digital signals
in the second memory means as the coefficients at the different terminals
in the sixth means.
20. Apparatus as set forth in claim 18, including,
the fifth means including sixth means for operating upon the digital
signals stored in the memory means in the second pseudo random code from
the second means and upon the digital signals produced in the fifth means
in representation of the updated values at the different terminals in the
third means and upon the digital signals representing the difference from
the fourth means for providing first digital signals and including seventh
means for operating upon the first digital signals and the digital signals
stored in the memory means in the second pseudo random code from the
second means to produce the digital signals representing the individual
coefficients at the different terminals of the third means.
21. Apparatus as set forth in claim 19, including,
the fifth means including ninth means for operating upon the digital
signals stored in the memory means in the second pseudo random code from
the second means and the upon the digital signals produced in the fifth
means in the representation of the updated values at the different
terminals in the third means and upon the digital signals representing the
difference from the fourth means for providing first digital signals and
including tenth means for operating upon the first digital signals and the
digital signals stored in the memory means in the second pseudo random
code from the second means to produce the digital signals representing the
updated values of the coefficients at the different terminals of the third
means,
the eighth means including eleventh means for operating upon the digital
signals stored in the memory means in the second pseudo random code from
the second means and upon the digital signals produced in the eighth means
in representation of the updated values at the different terminals in the
sixth means and upon the digital signals representing the difference from
the seventh means for providing second digital signals and including
twelfth means for operating upon the second digital signals and the
digital signals stored in the memory means in the second pseudo random
code from the second means to produce the digital signals representing the
individual coefficients at the different terminals of the sixth means.
22. Apparatus as recited in claim 18, including,
sixth means for operating upon the digital signals representing the
differences from the fourth means for producing digital signals
representing the data transmitted in the first pseudo random code from the
transmitter to the receiver.
23. Apparatus as recited in claim 19, including,
ninth means for operating upon the digital signals representing the
differences from the seventh means for producing digital signals
representing the data transmitted in the first pseudo random code from the
transmitter to the receiver.
24. Apparatus for use at a receiver for receiving through telephone lines
from a transmitter analog signals corresponding to digital signals
representing data in accordance with a plurality of analog levels and
modulated in a first pseudo random code involving the analog levels, the
received signals including echoes of analog signals transmitted from the
receiver to the transmitter and reflected from the transmitter back to the
receiver and modulated in a second pseudo random pattern different from
the first pseudo random pattern, including,
first means for providing digital signals representing the analog signals
received in the first and second pseudo random codes from the transmitter,
second means for providing digital signals modulated in the second pseudo
random code,
a first echo canceller responsive to the digital signals in the second
pseudo random code from the second means and having a first plurality of
terminals with individual coefficients at such terminals for adjusting
such digital signals in accordance with such individual coefficients,
third means responsive to the digital signals in the first and second
random codes from the first means and the adjusted digital signals in the
second pseudo random code from the first echo canceller for producing
digital signals representing the difference in the digital signals from
the first means and the first echo canceller,
the first echo canceller being operative to modify the digital signals
representing the individual coefficients at the terminals in the first
plurality in accordance with the digital signals from the third means,
a second echo canceller responsive to the digital signals in the second
pseudo random code from the second means and having a second plurality of
terminals, less than the first plurality, with individual coefficients at
such terminals for adjusting such digital signals in accordance with such
individual coefficients at the second plurality of terminals, and
fourth means responsive to the digital signals representing the difference
from the third means and the adjusted digital signals from the second echo
canceller for producing digital signals representing the difference in the
digital signals from the third means and the second echo canceller,
the second echo canceller being operative to modify the digital signals
representing the individual coefficients at the terminals in the second
plurality in accordance with the digital signals from the fourth means.
25. Apparatus as set forth in claim 24 wherein
the third means combines in a first particular relationship the values
represented by the digital signals in the first and second pseudo random
codes from the first means and the adjusted digital signals from the first
echo canceller to produce digital signals for modifying in the first echo
canceler the digital signals representing the coefficients at the
terminals in the first echo canceller and wherein
the fourth means combines in the second particular relationship the values
represented by the digital signals from the third means and the adjusted
digital signals from the second echo canceller to produce digital signals
for modifying in the second echo canceler the digital signals representing
the coefficients at the terminals in the second canceller.
26. Apparatus as set forth in claim 25 wherein
memory means are provided and wherein
the digital signals in the second pseudo random code are recorded in the
memory means and are thereafter reproduced from the memory means for
introduction to the first and second echo cancellers and wherein
the adjusted digital signals representing the individual coefficients in
the first and second echo cancellers are recorded in the memory means and
are thereafter reproduced from the memory means for respective
introduction to the third means and the fourth means.
27. Apparatus as set forth in claim 26 wherein
the third means combines in a first particular relationship the values
represented by the digital signals in the first and second pseudo random
codes from the first means and the adjusted digital signals from the first
echo canceller to produce digital signals for adjusting the digital
signals representing the coefficients at the terminals in the first echo
canceller and wherein
the fourth means combines in a second particular relationship the values
represented by the digital signals from the third means and the adjusted
digital signals from the second echo canceller to produce digital signals
for adjusting the digital signals representing the coefficients at the
terminals in the second canceller.
28. Apparatus for use at a receiver for receiving through telephone lines
from a transmitter analog signals corresponding to digital signals
representing data in accordance with a plurality of analog values and
modulated in a first pseudo random code involving the analog levels, the
received signals including echoes of analog signals transmitted from the
receiver to the transmitter and reflected from the transmitter back to the
receiver and modulated in a second pseudo random pattern different from
the first pseudo random pattern, including,
first means for providing digital signals representing the analog signals
received in the first and second pseudo random codes from the transmitter,
second means for providing digital signals modulated in the second pseudo
random code,
a memory,
third means for recording the digital signals from the second means in the
memory,
an echo canceller having a plurality of terminals with individual
coefficients at such terminals for modifying the digital signals in the
memory in accordance with such individual coefficients,
fourth means responsive to the digital signals in the first and second
pseudo random codes from the first means and the modified digital signals
from the echo canceller for providing digital signals representing the
difference between the digital signals from the first means and the
modified digital signals from the echo canceller,
fifth means responsive to the digital signals from the fourth means and the
digital signals representing the coefficients in the echo canceller for
modifying the digital signals representing the coefficients in the echo
canceller in accordance with the digital signals from the fourth means to
obtain updated coefficients in the echo canceller, and
sixth means for recording in the memory the modified digital signals from
the fifth means for use in the fourth means of such modified digital
signals from the echo canceller in providing the digital signals
representing the difference between the digital signals from the first
means and the modified digital signals from the echo canceller.
29. An apparatus as set fourth in claim 28, including,
sixth means responsive to the digital signals from the fourth means for
recovering the data represented by the analog signals transmitted in the
first pseudo random code from the transmitter to the receiver.
30. An apparatus as set forth in claim 29 wherein
the digital signals from the transmitter are initially in a third pseudo
random code with a limited number of analog values and wherein a
scrambler-descrambler is initially operative at the receiver as a
scrambler to synchronize the operation of the fourth means with the
signals in the third pseudo random code and wherein
the digital signals from the transmitter are subsequently in the first
pseudo random code and wherein the scrambler-descrambler is subsequently
operative at the receiver as a descrambler to provide for the recovery of
the data from the digital signals from the fourth means.
31. An apparatus as set forth in claim 29 including
the fifth means being operative to combine in a particular relationship the
digital signals from the fourth means and the modified digital signals
recorded in the memory to obtain the modified digital signals representing
the updated coefficients in the echo canceller.
32. A method at a receiver of receiving through telephone lines from a
transmitter analog signals corresponding to digital signals representing
data in accordance with a plurality of analog values and modulated in a
first pseudo random code involving the analog levels, the received signals
including echoes of analog signals transmitted from the receiver to the
transmitter and reflected from the transmitter to the receiver and
modulated in a second pseudo random pattern different from the first
pseudo random pattern, including the steps of:
receiving from the transmitter the analog signals modulated in the first
and second pseudo random codes,
converting such analog signals to corresponding digital signals,
providing digital signals modulated in the second pseudo random code,
providing digital signals representing a plurality of coefficients in a
first echo canceller,
modifying the digital signals modulated in the second pseudo random code in
accordance with the digital signals representing the coefficients in the
first echo canceller,
providing digital signals representing a first difference between the
converted digital signals and the modified digital signals modulated in
the second pseudo random code,
modifying the digital signals representing the coefficients in the first
echo canceller in accordance with the digital signals representing such
first difference,
providing digital signals representing a plurality of coefficients in a
second echo canceller, the plurality of coefficients in the second echo
canceller being less than the plurality of coefficients in the first echo
canceller,
modifying the digital signals modulated in the second pseudo random code in
accordance with the digital signals representing the coefficients in the
second echo canceller,
providing digital signals representing a second difference, the second
difference being between the digital signals modified in accordance with
the coefficients in the second echo canceller and the digital signals
representing the first difference, and
modifying the digital signals representing the coefficients in the second
echo canceller in accordance with the digital signals representing the
second difference.
33. A method as set forth in claim 32 including the step of:
recovering the data from the digital signals representing the second
difference.
34. A method as set forth in claim 32 wherein
the digital signals representing the modified coefficients in the first
canceller are recorded in a first memory and are subsequently read from
the first memory for modifying the digital signals modulated in the second
pseudo random code and wherein the digital signals representing the
modified coefficients in the second echo canceller are recorded in a
second memory and are subsequently read from the second memory for
modifying the digital signals modulated in the second pseudo random code
and wherein
the digital signals modulated in the second pseudo random code are recorded
in the first and second memories and are subsequently read from the first
and second memories for modifying the digital signals representing the
coefficients in the first and second echo cancellers.
35. A method as set forth in claim 33 wherein
the digital signals from the transmitter are initially in a third pseudo
random code with a limited number of analog values and wherein a
scrambler-descrambler is initially operative at the receiver as a
scrambler to synchronize the operation of the receiver with the digital
signals in the third pseudo random code and wherein
the digital signals from the transmitter are subsequently in the first
pseudo random code and wherein the scrambler-descrambler is subsequently
operative at the receiver as a descrambler to provide for the recovery of
the data from the digital signals representing the difference between the
modified digital signals in the second echo canceller and the digital
signals representing the difference.
36. Apparatus as set forth in claim 15,
thirteenth means for storing the digital signals from the tenth means in
the memory means,
the ninth means being responsive to the digital signals stored in the
memory means from the tenth means and the digital signals modulated in the
second pseudo random code from the second means for providing adjusted
digital signals in the second pseudo random code.
37. A method at a receiver of receiving through telephone lines from a
transmitter analog signals corresponding to digital signals representing
data in accordance with a plurality of analog values and modulated in a
first pseudo random code involving the analog levels, the received signals
including echoes of analog signals transmitted from the receiver to the
transmitter and reflected from the transmitter to the receiver and
modulated in a second pseudo random pattern different from the first
pseudo random pattern, including the steps of:
receiving from the transmitter the analog signals modulated in the first
and second pseudo random codes,
converting such analog signals to corresponding digital signals,
providing digital signals modulated in the second pseudo random code,
providing digital signals representing a plurality of different
coefficients in an echo canceller,
modifying the digital signals modulated in the second pseudo random code in
accordance with the digital signals representing the coefficients in the
echo canceller,
providing digital signals representing a difference between the converted
digital signals and the modified digital signals modulated in the second
pseudo random code,
modifying the digital signals representing the coefficients in the echo
canceller in accordance with the digital signals representing such
difference,
recording in a memory the digital signals modulated in the second pseudo
random code and the modified digital signals representing the coefficients
in the echo canceller,
thereafter using the digital signals recorded in the memory to provide the
digital signals representing the difference between the converted digital
signals and the modified digital signals modulated in the second pseudo
random code.
38. A method as set forth in claim 37, including the step of:
recovering the data from the digital signals representing the difference
between the converted digital signals and the modified digital signals
modulated in the second pseudo random code.
39. A method as set forth in claim 37, including the step of:
thereafter modifying the digital signals representing the coefficients in
the echo canceller in accordance with the digital signals thereafter
representing the difference, and
substituting in the memory the digital signals thereafter modified in
representation of the coefficients in the echo canceller in place of the
modified digital signals previously recorded in the memory.
40. A method as set forth in claim 37, including the steps of:
the echo canceller constituting a first echo canceller and the digital
signals representing the difference actually being in representation of a
first difference,
providing digital signals representing a plurality of different
coefficients in a second echo canceller, the plurality of coefficients in
the second echo canceller being less than the plurality of coefficients in
the first echo canceller,
modifying the digital signals modulated in the second pseudo random code in
accordance with the digital signals representing the coefficients in the
second echo canceller,
providing digital signals representing a second difference, the second
difference being between the digital signals modified in accordance with
the coefficients in the second echo canceller and the digital signals
representing the first difference,
modifying the digital signals representing the coefficients in the second
echo canceller in accordance with the digital signals representing the
second difference,
the memory being a first memory,
recording in a second memory the digital signals modulated in the second
pseudo random code and the modified digital signals representing the
coefficients in the second echo canceller, and
thereafter using the digital signal recorded in the second memory to
provide the digital signals representing the second difference.
41. A method as set forth in claim 40, including the steps of:
thereafter modifying the digital signals representing the coefficients in
the first echo canceller in accordance with the digital signals thereafter
representing the first difference,
substituting in the first memory the digital signals thereafter modified in
representation of the coefficients in the first echo canceller in place of
the modified digital signals previously recorded in the first memory,
thereafter modifying the digital signals representing the coefficients in
the second echo canceller in accordance with the digital signals
thereafter representing the second difference, and
substituting in the second memory the digital signals thereafter modified
in representation of the coefficients in the second echo canceller in
place of the modified digital signals previously recorded in the second
memory.
42. A method as set forth in claim 41, including the step of:
recovering the data from the digital signals representing the second
difference. |
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Claims |
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