Signalling techniques and device for high speed data transmission over voiceband channels

摘要

The present method (200,300, 400) and device (500, 600, 700) modify phase two of the format set forth in the V.34 Recommendation of the International Telecommunication Union-Telecommunication Standardization Sector to prevent premature disconnection of calls between a call modem and an answer modem. The method and device efficiently ensure connection of the call for high speed data transmission over voiceband channels, by modification of one of: a phase preliminary to phase one and phase two. One implementation, in the answer modem, includes transmitting a signal having first information, followed by a Signal S comprising of aguard tone and a signal S1, wherein an energy of a predetermined guard tone is greater than an energy of a predetermined range of frequencies of the Signal S1; and continuing transmitting and receiving in accordance with the modified V.34 operation.