What Does Digital Simultaneous Voice and Data Mean?
Digital simultaneous voice and data (DSVD) is a technology developed in mid 1990s using a technique supported only by certain modems. It multiplexes compressed speech with digital data for transmission across normal leased telephone lines.
Techopedia Explains Digital Simultaneous Voice and Data
DSVD capable modems engage in point to point data transmission and conversation. However, only when the Internet and the telephone are from the same service provider can DSVD enabled dial-up modems allow users to make or receive voice calls. Otherwise, special equipment from the telco is needed in place of a normal subscriber line interface circuit. Such services can also be supported through VoIP, DSL or ISDN over same wires as analog POTS lines. But these services do not define standards for carrying voice and data traffic simultaneously over interfaces between modems and computers.
The DSVD technology is endorsed mainly by Hayes, Intel, US Robotics and others, who have submitted it to ITU for standardization. These companies have minimized the gaps between narrow broadband communications links. And they have enabled users to control voice and data capability through GSM channels and other connections.