Method, including monitoring an audio signal on a telephone line with a detector and detecting an energy pulse in the audio signal on the telephone line; processing the energy pulse with a processor, where the energy pulse comprises a plurality of frequency components; determining a length of the energy pulse on the telephone line; calculating a phase for each of the plurality of frequency components to generate a plurality of phase values; generating a signal if the plurality of phase values are linear and if the length of the energy pulse is less than 40 milliseconds, where the signal is indicative that the plurality of phase values are linear and that the length of the energy pulse is less than 40 milliseconds, and further indicative that the signal is a three-way call attempt on the telephone line; and transmitting the signal to a host computer.