A method for data communication from a vehicle using a voice channel of a digital wireless telecommunications network comprising the steps of: providing an In-Vehicle System including an in-band signaling modem in a vehicle for mobile, wireless voice and data communication, both the voice and data communications to occur over a single voice call via a voice channel of a digital wireless communication network; the vehicle further including an in-vehicle audio system for entertainment and communication uses; the in-vehicle audio system including a speaker and microphone; deploying a customer software application in the In-Vehicle System, the customer software application coupled to the in-band signaling modem for sending data via the in-band signaling modem during a voice call; in the In-Vehicle System, initiating a voice channel call via the digital wireless communication network to a remote call taker location; at the call taker location, receiving the voice channel call initiated from the In-Vehicle System; sending a predetermined signaling tone from the call taker location, via the voice channel call, to the In-Vehicle System preparatory to an in-band data session; and in the In-Vehicle System, responsive to receiving the predetermined signaling tone, muting the audio system speaker so that occupants of the vehicle will not hear the sounds of data transferring in the form of audio frequency tones between the customer software application and the call taker location, wherein said predetermined signaling tone alternates among a plurality of initiating signals selected for compatibility with known vocoders, each initiating signal passing through a corresponding known vocoder. providing an In-Vehicle System including an in-band signaling modem in a vehicle for mobile, wireless voice and data communication, both the voice and data communications to occur over a single voice call via a voice channel of a digital wireless communication network; the vehicle further including an in-vehicle audio system for entertainment and communication uses; the in-vehicle audio system including a speaker and microphone; deploying a customer software application in the In-Vehicle System, the customer software application coupled to the in-band signaling modem for sending data via the in-band signaling modem during a voice call; in the In-Vehicle System, initiating a voice channel call via the digital wireless communication network to a remote call taker location; at the call taker location, receiving the voice channel call initiated from the In-Vehicle System; sending a predetermined signaling tone from the call taker location, via the voice channel call, to the In-Vehicle System preparatory to an in-band data session; and in the In-Vehicle System, responsive to receiving the predetermined signaling tone, muting the audio system speaker so that occupants of the vehicle will not hear the sounds of data transferring in the form of audio frequency tones between the customer software application and the call taker location, wherein said predetermined signaling tone alternates among a plurality of initiating signals selected for compatibility with known vocoders, each initiating signal passing through a corresponding known vocoder.