Local communication system and apparatus for use therein

An adapter device for connecting a first digital data processing circuit to a second digital data processing circuit via a wired communications link, the adapter comprising a self-contained unit including:

• analogue signal generating means for generating plural sine wave signals at a carrier frequency, the signals having predetermined different phases relative to one another;
• clock generating means connected with said analogue signal generating means for generating at least one digital clock signal synchronised with at least one of said sine wave signals for application to said first digital data processing circuit;
• switching means connected for receiving from said first digital data processing circuit a first digital serial data signal and for generating a first phase shift keying (PSK) modulated signal in accordance with the received first digital serial data signal by switching between different ones of said plural sine wave signals in response to transitions of said first digital serial data signal.

An adapter for connecting a first digital data processing circuit to a second digital data processing circuit via a wired communications link, the adapter comprising a self-contained unit including:

• carrier signal generating means for generating a carrier signal at a carrier frequency;
• clock generating means connected with said carrier signal generating means for generating at least one digital clock signal synchronised with said carrier signal for application to said digital data processing circuit;
• phase shift keying (PSK) modulation means for receiving from said first digital data processing circuit a first digital serial data signal and for generating a first PSK modulated signal in accordance with the received first digital serial data signal by selectively outputting one of (a) said carrier signal and (b) its inverse, dependent on the value of said first digital serial data signal.