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Telephone line carrier system

  • US 4,807,225 A
  • Filed: 02/02/1987
  • Issued: 02/21/1989
  • Est. Priority Date: 02/02/1987
  • Status: Expired due to Term
First Claim
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1. Telephone station apparatus for use at a subscriber'"'"'s premises, adapted to be parallel connected onto a first wire-pair that extends between said premises and a telephone line switching system, the apparatus including means for transmitting and receiving electrical signals substantially in a frequency band below 4 kHz,CHARACTERIZED BY:

  • a first modulator, having input and output ports, responsive to the transmitting means for converting electrical signals at its input port and in the frequency band below 4 kHz into electrical signals in a first frequency band above 4 kHz at its output port;

    means interconnecting the output port of the first modulator with the first wire-pair;

    a first demodulator, having an input port connected to the first wire-pair, for converting signals at its input port and in a second frequency band above 4 kHz into electrical signals in the frequency band below 4 kHz at an output port thereof;

    means interconnecting the output port of the first demodulator with the receiving means;

    means responsive to one or more telephone station control signals or status indicators for encoding same into a digital data signal;

    a second mdoualtor, having input and output ports, responsive to the digital data signal at its input port for converting same into an electrical signal in a third frequency band above 4 kHz at its output port; and

    means interconnecting the output port of the second modulator with the first wire-pair, whereby additional channels are added to an existing wire-pair without interference with, or displacement of, voiceband services already present on the wire-pair.

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