Method and apparatus for multilevel encoding for a local area network

A method for communication of data over wire communications media capable of undesired emission of radio frequency energy, comprising the steps of:

• encoding an input data stream as a serial data stream;
• modulating said serial data stream as a multiple-amplitude-level signal according to an amplitude specified by a variable L at a preselected data rate, said data rate specifying a sequence of time intervals during which detection of a transition is indicative of a bit value, wherein a transition intervals represents a first bit value and wherein no transition between any defined amplitude levels represents a second bit value, said modulating comprising:
• `(a) maintaining an idle state for input of any data representing a zero bit;
• (b) under conditions of variables T=1, D=1 and L.revreaction.N, decrementing the variable L by 1, and unconditionally returning to the idle state;
• and
• (e) under conditions of T=0, D=1 and L=0, incrementing the variable L by 1, and setting variable T to 1, and unconditionally returning to the idle state;
• wherein variable T indicates whether the amplitude is increasing (T=1) or decreasing (T=0);
• variable L indicates the amplitude value in discrete increments (L=0,1,2,3, . . . ,N);
• variable N is the number of level minus 1 (Levels =N+1);
• and
• variable D is the data value 1 or zero (0) only;
• to produce a multiple-level transition code signal having a tailored emissions spectrum;
• and
• applying said multiple-level transition code signal to said communications media.