Method and apparatus for transmitting digital data and real-time digitalized voice information over a communications channel

A method of transmitting data during idle intervals of voice conversation transmitted over a communication channel in real time comprising:

• transmitting said voice conversation with interleaved data by,
• developing a plurality of pulse code modulated voice codewords which encode said voice conversation,
• assembling said voice codewords into code groups, each code group including a predetermined number of said codewords,
• monitoring voice activity of said voice conversation by monitoring said voice codewords of a said code group to identify idle frames containing voice codewords which encode said conversation but have no significant voice activity, p2 replacing, upon detection of an idle frame, the first voice codeword of a next succeeding code group which encodes said conversation with a data transfer codeword, said data transfer codeword being different from any said voice codeword,
• replacing, upon detection of an idle frame, the second and subsequent voice code words of the next succeeding code group with data codewords representing data to be transmitted;
• transmitting said code groups on said communication channel;
• and
• receiving said voice conversation with interleaved data and removing said data therefrom by,
• monitoring each said code groups received from said communication channel,
• examining the first said codeword of each said code group to determine if the first said codeword of each said transmitted code group is a data transfer codeword;
• to identify the remaining codewords of said code group as data codewords,
• converting all said codewords within said code group to an analog voice signal to complete transmission of said voice conversation when said first codeword is not a said data transfer codeword, and
• supplying the second and subsequent codewords within said code group, when said first codeword is a data transfer codeword, as a digital data string.

A system of transmitting digitalized voice and data over a communications channel as a combined data stream, said digitalized voice being formed by digitalizing a voice signal using an encoding protocol wherein various amplitude levels of said voice signal are each represented as an individual bit code, at least a first amplitude level being represented by at least first and second redundant bit codes, comprising:

• first input means for providing said digitalized voice signal;
• second input means for providing said data;
• voice activity monitor means, responsive to said first input means, for detecting idle periods in said digitalized voice signal and for producing an idle output representative thereof;
• signalling generator means, operatively connected to said first input means, for substituting, during at least an initial periodic time frame, said second redundant code for said first redundant code in said digitalized voice signal, and for developing said first redundant code as a data start signalling code when data is to be transmitted;
• switch means, operatively connected between said communications channel and said signalling generator means, first input means and second input means, for supplying one of said digitalized voice signal, said data or said data start signalling code to said communications channel;
• and
• control means, responsive to the output of said voice activity monitor means, for controlling said switch means, said control means connecting said switch means to said first input means to transmit said digitalized voice signal, and connecting said switch means to said second input to supply data to said communications channel, said control means further controlling said signalling generator means and connecting said switch means to said signalling generator means during said periodic time frame;
• said control means reconnecting said switch means to said first input means when an idle period is no longer detected in said digitalized voice.