1.2 Front-Panel Operation
1 – 7
1.2.3
Operating modes
The SR470 has several distinct operating modes. The most basic
mode distinction is between
direct state control
– where the shutter
is explicitly commanded to open or close –versus
triggered control
,
where a timed sequence is executed. In either of these modes, the
control signals can be derived from internal or external sources.
Pressing the front panel [Input Source] key, in the “Mode” section,
will cycle between the di
ff
erent operating modes.
1.2.3.1 Internal triggered mode
The SR470 is in the
internal triggered mode
when the front panel
indicator
INT TRIG
in the “Mode” section is illuminated.
This mode should be selected to control the shutter state indepen-
dently of the rear-panel TTL control input (
§
1.3.3); internal triggered
mode ignores that input.
While in this mode, timed sequences may be initiated by pressing
the front panel [
] (trigger) button. Direct state control of the shutter
is also allowed in this mode: the state can be changed by pressing
the [OPEN] or [CLOSE] keys.
Please see
§
1.2.4 for more about timed sequences.
1.2.3.2 External triggered mode
The SR470 is in the
external triggered mode
when the front panel
indicator
EXT TRIG
in the “Mode” section is illuminated.
In this mode, timed sequences may be initiated on the falling edge
of a signal connected to the rear-panel TTL control input. Pressing
the [
] (trigger) key while in
external triggered mode
will
force
an
immediate trigger and “
” will appear on the numeric
display.
Pressing either [
] (reset), [OPEN], or [CLOSE] are requests for man-
ual control that will force the instrument out of
EXT TRIG
mode and
back to the
INT TRIG
mode.
1.2.3.3 External level mode
The SR470 is in the
external level mode
when the front panel indicator
EXT LVL
in the “Mode” section is illuminated.
In this mode, the state of the shutter is controlled only by the
level
of the rear-panel TTL control input. When the input is high
(unasserted), the shutter is commanded to be in the
Normal
state.
SR470 Shutter Controller
