Patent ID: 6895086

Claim:
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 at least 3 db below an amplitude level of the measured line voltage for frequency band F 2 , a coupler for combining the low level white noise signal with 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; wherein said 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.