Method and apparatus for detection of a telephone CPE alerting signal
AssigneeVTech Telecommunications Limited
InventorsJulian Lee, Gary Louie
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Abstract
A method and apparatus for detecting a signaling tone within a communications channel, such as a telephone line, is presented. The energy level of the communications channel signal is measured at the frequency of the signaling tone and at one or more frequencies that are integer divisors of the signaling tone (i.e. at one or more subharmonics). The subharmonic energies are evaluated in determining whether the signaling tone is present. The technique can be implemented using a plurality of resonators and a comparator.
Claims20
A method for detecting a predetermined signaling tone within a signal conveyed by a communications channel, the method comprising the steps of:
- performing a first measurement of the energy of the communications channel signal at the frequency of the predetermined signaling tone;
- performing a second measurement of the energy of the communications channel signal at a frequency that is an integer divisor of the predetermined signaling tone frequency;
- determining that the signaling tone is present when the result of the first measurement exceeds a first threshold, where the first threshold is derived from the result of the second measurement.
A method for detecting a customer premises equipment alerting signal comprised of one or more signaling tones received on a telephone line by a telephone while voice or other audible communications are occurring on the telephone line, which method is comprised of the steps of:
- measuring the signal energies present on the telephone line at the frequencies of the one or more signaling tones;
- measuring the signal energies present at one or more sub-harmonic frequencies of each of the one or more signaling tones;
- determining that the alerting signal is present when the energy of each signaling tone frequency exceeds a threshold derived from the energies measured at the one or more sub-harmonic frequencies for each signaling tone.
A telephone alerting signal detector for detecting the presence of a signaling tone on a communications channel, the detector comprising:
- a signaling tone resonator tuned to the frequency of the signaling tone;
- one or more sub-harmonic resonators, each sub-harmonic resonator being tuned to a frequency that is an integer divisor of the signaling tone frequency;
- a comparator including inputs that are derived from the outputs of the signaling tone and sub-harmonic resonators, whereby the output of the comparator is indicative of the presence of the signaling tone if the signaling tone resonator output exceeds a first threshold derived from the sub-harmonic resonator outputs.
Dependencies are inferred from the claim text.