Two-wire full-duplex modem

A two-wire full-duplex modem in which data which are time-divided into a main channel and a secondary channel are scrambled, modulated, and thereafter sent by a 2 W-4 W conversion circuit to a two-wire line, following which an estimated echo component, which is calculated from scrambled data, is subtracted from a signal from the 2 W-4 W conversion circuit and the signal from the 2 W-4 W conversion circuit is demodulated, descrambled and separated into main data and secondary data, the two-wire full-duplex modem comprising:

• scrambling generator polynomial for scrambling the data for transmission to the two-wire line;
• descrambling generator polynomial for descrambling the data received from the two-wire line;
• and
• majority means, connected to the scrambling generator polynomial and descrambling generator polynomial, for outputting a majority signal by a predetermined number of bits of descrambled secondary channel data.

A two-wire full-duplex modem for transmitting main data and secondary data to a two-wire line and for receiving main data and secondary data from the two-wire line, the two-wire full-duplex modem comprising:

• a first polynomial generator scrambling main data and secondary data based upon a first polynomial and transmitting the scrambled main data and secondary data to the two-wire line by way of a 2 W-4 W conversion circuit;
• a second polynomial generator descrambling main data and secondary data based on a second polynomial received from the two-wire line by way of the 2 W-4 W conversion circuit, wherein the second polynomial is different from the first polynomial;
• and
• a line-trouble detector, coupled to the first polynomial generator and the second polynomial generator, detecting the number of inversion points of a signal level in the descrambled-secondary data per unit time period, and outputting a line-trouble signal which indicates that there is trouble on the two-wire line when the number of detected inversion points are more than a predetermined number.