In-band signaling for data communications over digital wireless telecommunications networks

A synchronizer, comprising:

• an input that samples first and second audio tones;
• a demodulator that generates a synchronization value by comparing the samples of the first audio tone with the samples of the second audio tone;
• and
• a synchronizer that synchronizes the demodulator by shifting a start time for the samples of the first and second audio tones until the demodulator generates an optimum synchronization value.

A multichannel inband signaling modem for communicating digital data over a voice channel of a telecommunications network, comprising:

• an input for receiving digital data;
• a first modulator that converts a first binary bit value in a first portion of the digital data into a first audio tone having a first frequency and converts a second binary bit value in the first portion of digital data into a second audio tone having a second frequency;
• a second modulator that converts the first binary bit value in a second portion of the digital data into a third audio tone having a third frequency and converts the second binary bit value in the second portion of the digital data into a fourth audio tone having a fourth frequency;
• and
• an output for outputting the audio tones over a voice channel of a digital wireless telecommunications network.

A multicarrier inband signaling modem for communicating digital data over a voice channel of a telecommunications network, comprising:

• an input for receiving digital data;
• multiple modulators that each convert binary values at associated bit locations in the digital data into different audio tones;
• and
• an output for outputting the audio tones over a voice channel of a digital telecommunications network.