A system and method is provided for determining position of a mobile transmitter, such as a cellular telephone. The transmitter transmits a first signal at a first frequency (such as a RACH signal) to first and second receiving stations. The receiving sites are located at known locations. The transmitter then transmits a second signal at a second frequency (such a traffic signal) to the first and second receiving stations. The phases of the first and second signals at the first and second receiving sites are measured. Using the measured phases and the first and second frequency values, a range difference is calculated. This range difference defines a first hyperbola having the first and second receiving stations as foci on which the transmitter is located. By repeating the procedure with a different pair of receiving sites, a second hyperbola can be determined. The intersection of the first and second hyperbolas define the position of the transmitter.