High speed data modems, well known in the art, are operable to transmit data at signaling rates of up to 28,800 bits per second over the general switched telephone network and on leased point-to-point two-wire telephone type circuits. High speed data modems are described in ITU-T recommendation V.34, entitled "Data Communication Over the Telephone Network", submitted to the telecommunication standardization sector of the International Telecommunication Union in September 1994. In order to obtain these high transmission rates, a transmitter of such modems includes a precoder operable to minimize (whiten) or compensate for noise in the communication channel which can affect the transmitted signal at such high rates. A receiver in a second modem receiving the transmission must include the necessary circuitry for reconstruction of the precoded signal.
This preceding of the data signals thus permits the attainment of high data transmission rates at high power levels and reduced signal distortion. However, these high-speed modems are unable to transmit and/or receive voice and data signal transmissions simultaneously.
It is nevertheless known to simultaneously transmit voice and data signals along a single communication line, as for example an analog telephone channel. The transmission of simultaneous voice/data signals is performed through modems specially constructed for transmitting and receiving such simultaneous signals. However, these modems are unable to transmit simultaneous voice/data signals at the high power rates and reduced distortion achievable by a modem which incorporates preceding of the data signal.
It would thus be desirable to provide a high speed simultaneous voice/data modem incorporating data precoding and that is capable of maintaining power levels above and distortion below that achievable by conventional simultaneous voice/data modems.