3-Way call detection system
View Patent ↗Disclosed herein is a three-way call detection system and method for detecting the addition of a third party to a pre-existing telephonic connection between a first party and a second party. The system comprises: a meter for measuring the amplitude of a line voltage of a telephonic connection between a first party and a second party, said line voltage having a frequency band F 1 ; a first filter to remove a frequency band F 2 from said line voltage and output a filtered signal, said frequency band F 2 being a subset of F 1 ; a white noise generator for generating a low level white noise signal with a frequency band that corresponds to F 2 and with an amplitude that is significantly below an amplitude level of the measured line voltage for frequency band F 2 ; a coupler for combining the low level white noise signal to the filtered signal, thereby outputting an additive line voltage; a second filter that passes only a portion of the additive line voltage, said signal that passes being referred to as the band-passed signal, said band-passed signal having a frequency range F 3 , said frequency band F 3 being a subset of F 1 and being inclusive of F 2 ; and a processor for processing the band-passed signal and determining a baseline amplitude level associated with a two-way call. The processor monitors the band-passed signal in the time domain for a shift in baseline amplitude level, which shift is associated with the addition of a third party to the telephonic connection. The white noise being added is preferably at least 3 dB below the amplitude level of the measured line voltage, more preferably at least 10 dB, more preferably at least 20 db, and most preferably 40 db below. The frequency band F 2 is selected from F 1 to be significantly large enough to permit more reliable detection, and yet small enough to be barely perceptible to the listener. For example, F 2 may comprise the frequencies from 1–2 KHz. An F 2 of 1–1.3 KHz. also functions well.
1. A three way call detection system for detecting the addition of a third party to an pre-existing telephonic connection between a first party and a second party, said system comprising:
a meter for measuring the amplitude of a line voltage of a telephonic connection between a first party and a second party, said line voltage having a frequency band F 1 ,
a first filter to remove a frequency band F 2 from said line voltage and output a filtered signal, said frequency band F 2 being a subset of F 1 ;
a white noise generator for generating a low level white noise signal with a frequency band that corresponds to F 2 and with an amplitude that is measurably less than an amplitude level of the measured line voltage for frequency band F 2 ,
a coupler to combine the low level white noise signal with the filtered signal, thereby outputting an additive line voltage;
a second filter that passes at least a portion of the additive line voltage and substantially all of the low level white noise signal that was added, said signal that passes being referred to as the band-passed signal; and
a processor for processing the band-passed signal and determining a baseline amplitude level associated with a two-way call;
wherein said processor monitors the band-passed signal in the time domain for a measurable shift in baseline amplitude level, which shift occurs when a third party is added to the telephonic connection.
2. The three way call detection system of claim 1 , wherein the coupler is selected from the group consisting of: a voltage adder, a summer, a signal combiner, and a processor preprogrammed with a function that adds two signals to form a combined signal.
3. The three way call detection system of claim 1 , wherein the coupler is a signal combiner.
4. The three way call detection system of claim 1 , wherein the coupler is a processor preprogrammed with a function that adds two signals to form a combined signal.
5. The three way call detection system of claim 1 , wherein the amplitude of the line voltage is measured at a location selected from the group consisting of: the location of the first party, a telephone switching station, and a telephone central office.
6. The three way call detection system of claim 1 , wherein the amplitude of the line voltage is measured at a telephone switching station.
7. The three way call detection system of claim 1 , wherein the amplitude of the line voltage is measured at a telephone central office.
8. The three way call detection system of claim 1 , wherein the first filter is selected from the group consisting of: a notch filter, a band reject filter, a digital signal processor, and a circuit that subtracts signals in frequency band F 2 from the amplitude of the line voltage in frequency band F 1 .
9. The three way call detection system of claim 1 , wherein the first filter is a band reject filter.
10. The three way call detection system of claim 1 , wherein the first filter is a digital signal processor that cancels signals within frequency band F 2 .
11. The three way call detection system of claim 1 , wherein the first filter is a circuit that subtracts the amplitude signal in frequency band F 2 from the amplitude of the line voltage in frequency band F 1 .
12. The three way call detection system of claim 1 , wherein the second filter is selected from the group consisting of: a band pass filter, a digital signal processor, and a circuit that removes a band of frequencies from the line voltage.
13. The three way call detection system of claim 1 , wherein the second filter is a band pass filter.
14. The three way call detection system of claim 1 , wherein the second filter is a digital signal processor that cancels a band of frequencies.
15. The three way call detection system of claim 1 , wherein the second filter is a circuit that removes a band of frequencies from the line voltage.
16. The three way call detection system of claim 1 , wherein the white noise generator is selected from the group consisting of: a white noise source coupled to a bandpass filter; and a digital signal processor that generates a noise signal with a frequency band corresponding to F 2 .
17. The three way call detection system of claim 1 , wherein the white noise generator is a white noise source coupled to a bandpass filter.
18. The three way call detection system of claim 1 , wherein the white noise generator is a digital signal processor that generates noise with a frequency band corresponding to F 2 .
19. The three way call detection system of claim 1 , wherein the meter is selected from the group consisting of: a voltmeter, a multimeter, and a measuring circuit.
20. A method of detecting the addition of a third party to an pre-existing telephonic connection between a first party and a second party, said method comprising:
measuring a line voltage for amplitude, said measured line voltage having a frequency band F 1 ;
filtering the measured line voltage to remove a frequency band F 2 to create a filtered signal, said frequency band F 2 being a subset of frequency band F 1 ;
generating a low level white noise signal with a frequency band that corresponds to F 2 and with an amplitude that is less than an amplitude level of the measured line voltage for frequency band F 2 ,
adding the low level white noise signal to the filtered signal to create an additive line voltage;
filtering the additive line voltage to pass at least a portion of the additive line voltage and substantially all of the low level white noise that was added, said signal that passes being referred to as the band-passed signal;
processing the band-passed signal to determine a baseline amplitude level associated with the characteristics of a two-way call;
monitoring the band-passed signal in the time domain for a shift in baseline amplitude level, that occurs when a third party is added to the previous two-party call.