Automatic switching between dsl and analog on a single rj-11 dsl/analog combo modem

Abstract

Standard analog modems (modulator-demodulator devices) are currently commonplace in the home and office environments, where they are used to enable electronic devices, such as personal computers, to transmit data over existing telephone lines (made of small gauge copper wire) to other electronic devices. Data is stored digitally in such devices, but is converted by an analog modem to be transmitted over the lines in analog form. A data stream is established between a sender (i.e., originating electronic device) and a receiver (i.e., receiving electronic device) by using the resources of an entire telecommunications system. In other words, data is transmitted from the sender's local loop, through the telephone switching system, and to the receiver's local loop. Because the lines used by analog modems to transmit data only use a frequency range of about 0–3400 Hz, a data transmittance limit of about 56,000 bits-per-second (bps) exists for communication through the lines. An analog modem operating at this high end may, for example, be a modem operating under the ITU V.90 standard.