Cross-frame dual tone multifrequency detector

A signal detector, comprising:

• a processor adapted to receive at least a first and second frame of time domain input samples;
• and
• a memory device coupled to the processor and adapted to store program instructions, that when executed by the processor:
• generate a first frequency energy value for the first frame, a second frequency energy value for the second frame, a third frequency energy value for the first frame and a fourth frequency energy value for the second frame based on the time domain input samples, wherein the first and second frequency energy values are associated with a first tone frequency, and the third and fourth frequency energy values are associated with a second tone frequency;
• compare a first frequency energy value associated with the first frame to a second frequency energy value associated with the second frame to determine the presence of a first tone in the time domain input samples and compare the third frequency energy value to the fourth frequency energy value to determine the presence of a second tone in the time domain input samples;
• determine a first twist between the first and third frequency energy values, determine a second twist between the second and fourth frequency energy values;
• and
• compare the first and second twists to determine the presence of the first and second tones.

A signal detector, comprising:

• a processor adapted to receive at least a first and a second frame of time domain input samples;
• and
• a memory device coupled to the processor and adapted to store program instructions, that when executed by the processor:
• generate at least one frequency energy value for each of the first and second frames based on the time domain input samples;
• compare a first frequency energy value associated with the first frame to a second frequency energy value associated with the second frame to determine the presence of a first tone in the time domain input samples;
• and
• scale the greater of the first and second frequency energy values to generate a scaled energy value and compare the scaled energy value to the lesser of the first and second frequency values to determine the presence of the first tone.

A method for detecting a signal, comprising:

• receiving at least a first and a second frame of time domain input samples;
• generating at least a first frequency energy value for the first frame and a second frequency energy value for the second frame based on the time domain input samples and a first tone frequency;
• generating at least a third frequency energy value for the first frame and a fourth frequency energy value for the second frame based on the time domain input samples and a second tone frequency;
• comparing the first frequency energy value to the second frequency energy value to determine the presence of a first tone in the time domain input samples;
• comparing the third frequency energy value to the fourth frequency energy value to determine the presence of a second tone in the time domain input samples;
• determining a first twist between the first and third frequency energy values;
• determining a second twist between the second and fourth frequency energy values;
• and
• comparing the first and second twists to determine the presence of the first and second tones.

A method for detecting a signal, comprising:

• receiving at least a first and a second frame of time domain input samples;
• generating at least a first frequency energy value for the first frame and a second frequency energy value for the second frame based on the time domain input samples;
• comparing the first frequency energy value to the second frequency energy value to determine the presence of a first tone in the time domain input samples;
• scaling the greater of the first and second frequency energy values to generate a scaled energy value;
• and
• comparing the scaled energy value to the lesser of the first and second frequency energy values to determine the presence of the first tone.

A method for detecting a signal, comprising:

• receiving at least a first and a second frame of time domain input samples;
• generating at least a first frequency energy value for the first frame and a second frequency energy value for the second frame based on the time domain input samples and a first tone frequency;
• generating at least a third frequency energy value for the first frame and a fourth frequency energy value for the second frame based on the time domain input samples and a second tone frequency;
• comparing the first frequency energy value to the second frequency energy value to determine the presence of a first tone in the time domain input samples;
• comparing the third frequency energy value to the fourth frequency energy value to determine the presence of a second tone in the time domain input samples;
• multiplying the first frequency energy value by the fourth frequency energy value to determine a first twist value;
• multiplying the second frequency energy value by the third frequency energy value to determine a second twist value;
• scaling the greater of the first and second twist values to determine a scaled twist value;
• and
• comparing the lesser of the first and second twist values to the scaled twist value to determine the presence of the first and second tones.

A method for detecting a signal, comprising:

• receiving at least a first and a second frame of time domain input samples;
• generating a plurality of frequency values for the first and second frames;
• determining a cross-frame twist ratio based on the plurality of frequency values;
• and
• determining the presence of a first tone and a second tone in the time domain input samples based on the cross-frame twist ratio.

A signal detector, comprising:

• a processor adapted to receive at least a first and a second frame of time domain input samples;
• and
• a memory device coupled to the processor and adapted to store program instructions, that when executed by the processor:
• generate a plurality of frequency values for the first and second frames;
• determine a cross-frame twist ratio based on the plurality of frequency values;
• and
• determine the presence of a first tone and a second tone in the time domain input samples based on the cross-frame twist ratio.

A signal detector, comprising:

• means for receiving at least a first and a second frame of time domain input samples;
• means for generating a plurality of frequency values for the first and second frames;
• means for determining a cross-frame twist ratio based on the plurality of frequency values;
• and
• means for determining the presence of a first tone and a second tone in the time domain input samples based on the cross-frame twist ratio.