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Aiming beam intensity is controlled by variable (digi-pot) resistance U3 on the Controller PCB connected to
the aiming beam module through J13-3 and J13-4. The microprocessor sets the aiming beam intensity to high,
low, or medium by changing the variable resistance (U3) using the /LASER_DIODE_STEP/ and /
LASER_DIODE_DIR/ digital I/O EPLD output lines.
4.4.9 Fiber and Blast Shield Position Sense Circuits
Refer to page 8-9 and 8-16 in Section 8 and the Fiber and Blast Shield Position Sense Simplified Diagram
(Fig. 4.7). The VersaPulse Select III will not allow treatment delivery if it senses that the blast shield is not
inserted or that a fiber is not properly attached.
The blast shield position is sensed by a microswitch that closes when the blast shield is properly inserted. A +5
VDC pull up from the Controller PCB is applied through the microswitch, back to the Controller PCB and on
to the microprocessor digital I/O EPLD through U49-20 on the Controller PCB (BLAST_SHIELD_IN). The
BLAST_SHIELD_IN signal is high when the blast shield is properly inserted. Note that when the blast shield
is properly inserted, LED11 will illuminate.
Correct fiber attachment is important to insure proper Z position of the focusing lens in relation to the end of
the fiber. As the fiber is screwed onto the SMA connector, it forces a spring loaded cover plate inwards
towards the fiber focus assembly. When the fiber is completely screwed down it provides an additional
electrical connection:
The cover plate activates a microswitch on J8-3, causing the switch to close. As the switch closes, a sig-
nal path is completed allowing the current to flow to ground. The signal /FIBER_IN_SW/ is asserted
to the input of U41-9 resulting in a FIBER_IN signal output. As the fiber face physically contacts the
SMA connector and fiber focus assembly housing, completing an electrical connection to ground for
the /FIBER_CONNECTED_SW/ line on J8-1. The /FIBER_CONNECTED_SW/ line is inverted to
become FIBER_CONNECTED. Both of these signals become input signals to the digital
I/O EPLD U49. Note that LED12 illuminates when /FIBER_IN_SW/ signal is low, and LED13 illumi-
nates when the /FIBER_CONNECTED_SW/ is low.
4.4.10 Service Attenuator Circuit
Refer to pages 8-9 and 8-14 in Section 8 and the Service Attenuator Simplified Diagram. The service
attenuator is inserted into the beam path during servicing to prevent damage to the end of an attached fiber
(including the blast shield) and also to protect the transimpedance amplifier during the fiber alignment. It is
used when the alignment of the YAG beam is not known to be good into the end of the fiber. The attenuator
provides greater than 99% attenuation. The servicing engineer can activate the service attenuator by sliding
SW4 on the Controller PCB. The microprocessor turns the service attenautor solenoid on, placing the
attenuator in the beam path. Position is sensed by a slotted optical switch, and when in the beam path, the
"ATTEN IN BEAM" message is displayed on the LCD color display. Note that LED26 illuminates when the
service attenuator is closed.
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