Rec. ITU-T G.165(11/1988) – ECHO CANCELLERS
1 General
2 Definitions relating to echo cancellers1
    2.1 echo canceller (see Figure 4/G.165)
    2.2 echo loss (A_ECHO)
    2.3 cancellation (A_CANC)
    2.4 residual echo level (L_RES)
    2.5 nonlinear processor (NLP)
    2.6 nonlinear processing loss (A_NLP)
    2.7 returned echo level (L_RET)
    2.8 combined loss (A_COM)
    2.9 convergence
    2.10 convergence time
    2.11 leak time
3 Characteristics of echo cancellers
    3.1 General
    3.2 Purpose, operation and environment
    3.3 External enabling/disabling
    3.4 Tests and requirements for performance with inputs signals applied to the send and receive paths
4 Characteristics of an echo canceller tone disabler
    4.1 General
    4.2 Disabler characteristics
    4.3 Guardband characteristics
    4.4 Holding-band characteristics
    4.5 Operate time
    4.6 False operation due to speech currents
    4.7 False operation due to data signals
    4.8 Release time
    4.9 Other considerations
5 Nonlinear processors for use in echo cancellers
    5.1 Scope
    5.2 General principles and guidelines
ANNEX A – Echo cancellers without nonlinear processing
ANNEX B – Description of an echo canceller reference tone disabler
B.1 General
B.2 Disabler characteristics
B.3 Guardband characteristics
B.4 Holding-band characteristics
B.5 Operate time
B.6 False operation due to speech currents
B.7 False operation due to data signals
B.8 Release time
ANNEX C – Description of a reference nonlinear processor
C.1 General
C.2 Suppression threshold (T_SUP)
C.3 Static characteristics of activation control
C.4 Dynamic characteristics of activation control
C.5 Frequency limits of control paths
C.6 Testing
Reference