Figure 4-1. PCM code definitions.
(1) The Bi codes may be
derived from the corresponding NRZ codes by inverting the level for the last
half of each bit interval.
(2) The definitions of the mark and space versions of the bi-phase code have
been reversed in various editions of the IRIG Telemetry Standards. The
Telemetry Group included both definitions in the 1986 and 1993 versions of the
Telemetry Standards. In 106-96, the Telemetry Group replaced the 106-93
Bi -M and
Bi -S definitions with
the 106-93 DBi-S and
DBi -M definitions. The
106-93 Bi -M and
DBi -S definitions were
identical except for a possible inversion and a time delay of one-half bit
period. The Bi -S and
DBi -M codes were identical
with the same exceptions. The inversions do not change the data content,
because the information is in the level changes (transitions) not the levels.
The differential terminology and code designation have been dropped.
|
