Transmission system with improved tone detection
AssigneeU.S. Philips Corporation
InventorsHarm Braams, Cornelis M. Moerman
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Abstract
In a transmission system, a signalling tone is transmitted by a transmitter to a receiver via a transmission channel. In the receiver, a tone detector detects the presence of a signalling tone. In order to improve a reliability of the tone detector, a number of correlating elements which determine a correlation value between an input signal and a reference signal are used. Absolute output signals of the correlating elements are added by an adder to derive a combined correlation signal to be used for detection.
Claims31
A transmission sytsem comprising a transmitter for transmitter for transmission of a tone via a transmission channel to a receiver, said receiver comprising a detector for detecting a presence of the tone ina received signal, wherein the detector comprises a correlator for deriving a combined correlation signal representative of a combination of a plurality of correlation signals each representative of a correlation value of the received signal and a selected one of a plurality of phase shifted reference signals.
A terminal comprising a detector for detecting a presence of a tone in a received signal, said detector comprising a correlator for deriving a combined correlation signal representative of a combination of a plurality of correlation signals each representative of a correlation value of the received signal and a selected one of a plurality of phase shifted reference signals.
A detector for detecting a presence of a tone in an input signal, said detector comprising a correlator for deriving a combined correlation signal representative of a combination of a plurality of correlation signals each representative of a correlation value of the input signal and a selected one of a plurality of phase shifted reference signals.
A method for detecting a presence of a tone in an input signal, said method comprising deriving a combined correlation signal representative of a combination of a plurality of correlation signals each representative of a correlation value of the input signal and a selected one of a plurality of phase shifted reference signals.
Dependencies are inferred from the claim text.