Give an account of modems used in data transfer.

Modem: Modems are usually provided through network operators (Department of Telecommunication in India) or through vendors who are not essentially the manufacturers of computer systems. Therefore, there is a requirement to standardize the interface in between the computer equipment and the modem. CCITT terminology for the modem is data circuit terminating equipment (DCE) and for the computer this is data terminal equipment (DTE). DCE is frequently referred to as data communication equipment, outer-side CCITT. This is significant to recognize that DCE and DTE are generic terms and may be applied to a variety of equipments not essentially only to modems or computers. For illustration, a DTE may be a workstation, a computer or terminal and a DCE may be a modem or a computer based node into a data network. A series of standards, termed as V-series, has been specified by CCITT for interfacing DTEs to DCEs operating along with public switched telephone networks.