Nautel XR6, Руководство по устранению неисправностей, Страница: 214 / 291

XR6/XR3 Troubleshooting Manual Reading Electrical Schematics
Page 5-2 Issue 3.0 2009-07-15
Unique symbols
Nautel uses unique symbols on electrical schematics to describe logic (two-state) signals. These
signals differ from single-state signals or analog signals that may have multiple values.
Type of inputs and outputs
On electrical schematics, names used to describe logic (two-state) input and output signals are
prefixed with a
#
symbol.
Logic level convention
The
#
symbol prefix identifies an input or output signal that has two distinct states:
high
and
low
.
The suffix on the signal name identifies the active (true) state of the signal. The
high
(+ suffix) is the
more positive of the two levels used to represent the logic states. The
low
(- suffix) is the less positive
of the two levels.
Two types of logic, positive and negative, may be represented on a particular schematic.
• In positive logic,
high
represents the active (true) state and
low
represents the inactive (false)
state.
• In negative logic,
low
represents the active (true) state and
high
represents the inactive
(false) state.
Identifying schematic diagrams
Each illustration in this section is identified by a number that is both the figure number and the page
number. The numbers are assigned sequentially and are prefixed by the letters ‘SD’. The electrical
schematics and logic diagrams included in this section are listed in
Table 5.1 on page 5-5 .