Model
8901B
Operation
Remote/Local
Mode Descriptions
Remote Mode.
In remote, the Modulation Analyzer’s front-panel controls are disabled except for the
LOCAL and CLEAR keys. The LOCAL and CLEAR keys are only disabled by Local Lockout. However,
front-panel displays and the output signal at MODULATION OUTPUT/AUDIO INPUT remain active
and valid.
Two
triggering modes are available in remote operation: Free Run and Trigger Hold.
Displays which time out in Local do not time out in Remote. In Remote operation, the CLEAR key
will clear the display and works as
a
trigger when Trigger Hold
is
used.
Local Mode.
In local, the Modulation Analyzer’s front-panel controls are fully operational. When the
Modulation Analyzer goes
to
local operation, the front-panel REMOTE annunciator turns
off.
However,
when the Modulation Analyzer
is
being addressed (whether in remote
or
local),
its
front-panel LISTEN
or TALK annunciator lights. Free Run
is
the only triggering mode available in local operation.
Mode Transitions
Local
to Remote Transitions.
The Modulation Analyzer switches
to
remote operation upon receipt
of the Remote message. No instrument settings are changed by the transition from local
to
remote.
The Tkigger mode will always be Free Run
(TO)
on entry
to
remote operation.
Remote to Local Transitions.
The Modulation Analyzer always switches
to
local from remote
whenever
it
receives the Local
or
the Clear Lockout/Set Local message.
No
instrument settings are
changed by the transition from remote
to
local, except the flrigger mode will always be reset
to
Free Run.
If
it
is not in Local Lockout mode, the Modulation Analyzer switches
to
local from remote whenever
its
front-panel LOCAL key
is
pressed.
NOTE
Remote to Local transitions
will
not clear a Service Request message.
Local
Lockout
Local lockout disables the LOCAL key (and the CLEAR key) and allows return-to-local only under
program control.
When a
data
transmission
is
interrupted, which can happen
if
the LOCAL key is pressed, the
data
being transmitted may be lost. This would leave the Modulation Analyzer in an unknown state. To
prevent this, a local lockout
is
recommended.
3-25
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