Lok-to-Clock Electronics
8-3
LEVEL indicator—displays relative photodiode signal strength with full-
scale = maximum signal. This is an uncalibrated reference indicator.
LEVEL control—allows you to adjust the photodiode input signal gain.
This control is typically fully clockwise (full on).
FREQUENCY: SELECT button—sets the frequency display to show either
the reference frequency (
REF—which can be either an internal or an exter-
nal reference source), the actual laser pulse frequency (LSR), or the differ-
ence between the two (DIF).
FREQUENCY: REF indicator—shows that it is the system reference fre-
quency that is being displayed.
FREQUENCY: LSR indicator—shows that it is the actual laser frequency,
as measured by the Tsunami laser photodiode output, that is being dis-
played.
FREQUENCY: DIF indicator—shows that it is the difference between the
reference frequency and actual laser pulse frequency that is being dis-
played.
FREQUENCY display panel—an 8-digit LED panel that displays either an
internal or external reference frequency (REF), the actual laser pulse fre-
quency (LSR), or the difference between the two (DIF). Frequency is shown
in MHz to the nearest 10 Hz. The display has a 1 Hz refresh rate.
FREQUENCY up/down push buttons—increases or decreases the laser
repetition rate by adjusting the laser cavity length via the M
1
motorized
micrometer.
STATUS indicator—a bar display that, when lit, shows the relative posi-
tion of the M
4
PZT mirror within its range. When no segments are lit, the
Lok-to-Clock function has been disengaged via the STATUS: LOCK button.
STATUS: LOCK push button—toggles the Lok-to-Clock PLL circuit on
and off. If the difference between the reference and the laser cavity fre-
quency is < 50 kHz when the LOCK button is pressed, the system will auto-
matically servo the M
1
motor micrometer in order to bring the frequency
difference within the locking range (< 100 Hz) of the PZT-controlled M
4
mirror. When LOCK is on, one or two segments of the STATUS bar display
are on.
POWER: ON indicator—shows that power is applied to the Model 3930
electronics module.
Rear Panel
Power cord connector—provides connection for a standard power cord.
Power switch—turns power on and off to the Model 3930. It is located
next to the power cord connector.
Voltage select switch—provides a means to match the electronics input
power to your local line voltage. Input voltage selections are 100, 120, 220,
and 240 Vac. Appendix C describes how to set the switch and select the
fuse rating for your line voltage.
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