Text telephone modem communications over packet networks

A first gateway capable of detecting a text telephone modem, said first gateway having a voice mode and a text telephone modem mode, said first gateway being capable of communicating with a second gateway over a packet network, said first gateway comprising:

• an encoder configured to encode an input signal using a first coding scheme to generate a first encoded input signal, while said first gateway is in said voice mode;
• a transmitter configured to transmit said first encoded input signal to said second gateway over said packet network, while said first gateway is in said voice mode;
• a detector configured to look for a first tone in said input signal while said first gateway is in said voice mode, wherein said first tone is indicative of a beginning of a text telephone modem character, and wherein said text telephone modem character comprises said first tone;
• wherein said detector is configured to detect said first tone in said input signal while looking for said first tone, wherein said first gateway is configured from said voice mode to said text telephone modem mode in response to detecting said first tone,
• wherein said first gateway is configured to provide a silence period, after a switching silence caused by said configuring said first gateway from said voice mode to said text telephone modem mode, so as to prevent a detection of said first encoded input signal by said second gateway as said beginning of said text telephone modem character;
• and
• wherein said transmitter is configured to transmit said input signal to said second gateway over said packet network, after said silence period, according to said text telephone modem mode.