�1���� Scope
�2���� References
�3���� Terms and
definitions
������� 3.1���� acoustic
echo
������� 3.2���� cancelled
end
������� 3.3���� combined
loss (ACOM)
������� 3.4���� comfort
noise
������� 3.5���� composite
echo
������� 3.6���� convergence
������� 3.7���� convergence
time
������� 3.8���� double-talk
������� 3.9���� echo
canceller
������ 3.10���� echo
cancellers in tandem
������ 3.11���� echo
path
������ 3.12���� echo
path capacity (∆)
������ 3.13���� echo
path delay (td)
������ 3.14���� echo
return loss (ERL) (AECHO)
������ 3.15���� echo
return loss enhancement (ERLE) (ACANC)�
������ 3.16���� electric
echo
������ 3.17���� H
register
������ 3.18���� H
register reset
������ 3.19���� leak
time
������ 3.20���� non-cancelled
end
������ 3.21���� non-linear
processor (NLP)
������ 3.22���� non-linear
processing loss (ANLP)
������ 3.23���� open
echo path
������ 3.24���� pure
delay (tr)
������ 3.25���� residual
echo level (LRES)
������ 3.26���� returned
echo level (LRET)
������ 3.27���� signal
processing device (SPD)
������ 3.28���� signal
processing function (SPF)
������ 3.29���� signal
processing network equipment/element (SPNE)
�4���� Abbreviations
and acronyms
�5���� Test signals
�6���� Characteristics
of echo cancellers
������� 6.1���� General
������� 6.2���� Purpose,
operation and environment
������� 6.3���� External
enabling/disabling
������� 6.4���� Tests
and requirements for performance with input signals applied to the send and receive
paths
�7���� Characteristics
of an echo canceller tone disabler
������� 7.1���� General
������� 7.2���� Detector
characteristics
������� 7.3���� Guardband
characteristics
������� 7.4���� Holding-band
characteristics
������� 7.5���� Operate
time
������� 7.6���� False
operation due to speech currents
������� 7.7���� False
operation due to data signals
������� 7.8���� Release
time
������� 7.9���� Other
considerations
�8���� Non-linear
processors (NLPs) for use in echo cancellers
������ �8.1���� Scope
������� 8.2���� General
principles and guidelines
Annex A � Description of an echo canceller reference
tone disabler
Annex B � Description of a reference non-linear
processor
������� B.1���� General
������� B.2���� Suppression
threshold (TSUP)
������� B.3���� Static
characteristics of activation control
������� B.4���� Dynamic
characteristics of activation control
������� B.5���� Frequency
limits of control paths
������� B.6���� Testing
Annex C � Composite source signals for testing of
speech echo cancellers � Signal, description and analysis
������� C.1���� Introduction
������� C.2���� Composite
source signal � General considerations
������� C.3���� Bandlimited
composite source signal with speech like power density spectrum � Practical
realization for measurements of echo cancellers����
������� C.4���� Appropriate
analyses to determine convergence characteristics of speech echo cancellers
using the composite source signal
Annex D � Echo-path models for testing of speech echo
cancellers
������� D.1���� Introduction
������� D.2���� Echo path
models from network hybrid simulator
������� D.3���� Echo path
models measured from telephone networks in North America
������� D.4���� Echo path
models measured from telephone networks in Europe��
Annex E � Embedded Echo Cancellers (EECs)
������� E.1���� Scope
������� E.2���� Definitions
������� E.3���� EEC
requirements
����� Page
������� E.4���� EEC
testing
������� E.5���� Special
considerations
Appendix I � Guidance for application of echo
cancellers
������� I.1���� Scope
������� I.2���� Echo
control in the public switched telephone network�
������� I.3���� Application
rules and operational constraints
������� I.4���� Effect
of cancellers on voice and data services
������� I.5���� High-level
speech
������� I.6���� Network
and service evolutionary considerations
������� I.7���� Considerations
regarding echo canceller performance during double talk
Appendix II � Measurement methods for characteristics
of echo paths
������ II.1���� Introduction
������ II.2���� Measurement
procedure
������ II.3���� Analysis
of echo-path characteristics
������ II.4���� Examples
of echo path measurements from real networks
������ II.5 ����Conclusions
Appendix III � Multiple tail circuits
Appendix IV � Guidelines on the use of parameters for
testing echo cancellers
Appendix V � List of low speed modems for optional use
with Test No. 14
Appendix VI � Example control interfaces
������ VI.1���� Parallel
transistor-transistor logic (TTL) connection for digital signals
������ VI.2���� Serial
data link (ITU-T V.24 or RS-232) for software commands
Appendix VII � Guidance on echo canceller orientation
in conference bridge applications
����� VII.1���� Introduction
����� VII.2���� Echo
canceller oriented towards the hybrid of the conference bridge participant
(recommended)
����� VII.3���� Echo
canceller oriented away from the hybrid of the conference bridge participant
(not recommended)
Appendix VIII � Test methodologies for use on embedded
echo cancellers
���� VIII.1���� Introduction
���� VIII.2���� Test
Methodology 1: Testing with the aid of a special "Test Mode" (under
study)
���� VIII.3���� Test
Methodology 2: Testing without access to control signals (under study)
Bibliography