Tone signalling with tfo communication links

Method of conveying information tone signaling through a link Digital Circuit Multiplication Equipment - Equipment digital circuit multiplication, TFO, specific to GSM, in a GSM network that supports Tandem Free Operation - Operation No Tandem, TFO, and modes of speech compression for the passage of signals through the link, using respectively TFO frames and the like frames to TRAU, the method comprising: detecting (6a), in a data stream to the local entrance to the TFO link, one DTMF signal to be transported, coding the tone signal detected in bits of a TFO or similar to TRAU to be sent through the TFO link, including adjusting the bit to mark the plot as having a signaling information tones and setting bits to identify the DTMF signal detected in the information tone signaling is carried in-band through the TFO link as a TFO or similar to TRAU checked, detecting (7a), in remote output TFO link, the marked frame and regenerating the tone signal, depending on the bits of the frame marked.