Polaroid Joshua Vision Service Manual page 62

mechanical and electronic components. Because electronic noise is developed during each cycle of the
Joshua camera, gating circuitry has been added to the horn assembly to eliminate any developed noise
during an Ambient or Strobe Exposure Test.
This horn assembly has five (5) external components: Two switches (SW 1 and SW 2), two LED's (Green and
Red) and one photo transistor. Switch 1 (SW 1) is used to toggle from its Strobe to Ambient mode of
operation. The two LED's indicate the state of the Strobe mode. The green LED lights to indicate when the
Strobe mode is in its ready state. The red LED lights to indicate when the Strobe mode is in its not ready
state. Pushbutton switch 2 (SW 2) can be used to place the Strobe mode in its ready state.
During the Strobe mode of operation, the photo transistor detects both the wink and strobe pulse. The Green
and Red LED's turn on/off during this period (this is part of the gating function of the horn assembly).
For Ambient measurements, Switch 1 (SW 1) must be set to its Ambient (AMB) position. The internal
electronics of the horn assembly controls the gating function for the Ambient mode of operation.
HORN
SWITCH 1
RED LED
GREEN LED
SWITCH 2
Figure 3-2. Joshua Horn Assembly
Alignment Gauge
The alignment Gauge (Figure 3-4) is used in place of the 640 Nest Assembly on the Star Tester for the
Joshua camera. It references the Joshua camera photocell and taking lens of the camera to the light source
of the Star tester.
Base Riser
The Base Riser (Figure 3-4) is used to vertically align the Joshua camera to the Star Tester. If the Star
Tester has leg risers, the Base Riser must be used. If it does not have leg risers, the Base Riser should not be
used.
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