Telephonic communications – Supervisory or control line signaling – Signal receiver
Patent
1996-01-31
1998-09-29
Matar, Ahmad F.
Telephonic communications
Supervisory or control line signaling
Signal receiver
379406, 379410, H04J 1500
Patent
active
058155686
ABSTRACT:
A method and apparatus for determining when an echo canceller should be disabled in a telephoning system is disclosed. First, a first power estimate is determined from an input signal. In addition, the input signal is divided into in-phase and quadrature components. The in-phase and quadrature components are then subsampled and used to determine a second power estimate. The first and second power estimates are compared to determine whether a predetermined tone is present. When the predetermined tone is detected, the present invention determines whether a phase reversal in the predetermined tone is present by using the in-phase and quadrature components. When the phase reversal is detected, the echo cancellers are disabled.
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Matar Ahmad F.
Telefoanktiebolaget LM Ericsson
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