Telephone handset interface for automatic switching between voice and data communications

摘要

A telephone interface system is inserted between the telephone handset and base to provide automatic switching between voice and data modes of communication. The interface includes a modem having a receive port coupled to the telephone base speaker lines and a transmit port switchably coupled to the base microphone lines, a switch for selectively coupling the telephone handset to the base, and a processor for monitoring data received by the modem and controlling the switch to automatically decouple the telephone handset from the base when data is being received or transmitted by the modem. The modem includes a tone generator that generates a predetermined start signal to signal a remote unit at the other end of the communication link to enter data mode prior to transmission of data. Similarly, the modem includes a tone detector to detect a start signal sent by the remote unit that causes the unit to switch into data mode in preparation for receiving data. The start signal can also include signals designating the rate at which data will be transmitted and its format.