A method and system for modem signaling over a voice channel of a cellular or other wireless communication system. A plurality of sequential tones are transmitted, each of which corresponds to at least one network type and contains at least one primary frequency selected so as to successfully be passed through its associated network type. This permits the use of modem signaling to establish a data connection regardless of the type of network equipment utilized, so that the method will work with both newer and older generation vocoders and other network equipment.