numbered. Refer to these numbers while you read the
following section.
1. The GRAY SCALE switch energizes the
circuit in the power supply-video converter WRA,
which presents ten shades of gray across the bottom
of the video indicator.
2. The MODE switch is a 6-position rotary
switch that selects the mode of operation. In the
STBY position, the system is maintained in the
operational readiness state. The air conditioning and
cryogenic cooling of detectors is activated. The
receiver head is in the stow position (CCW and up
limits).
3. The AZIMUTH knob controls the receiver
slew signals (azimuth) in the position mode of
operation.
4. The SYS GO push button illuminates to
indicate a good system at the completion of BITE.
The light can be extinguished by pressing the
indicator.
5. The BIT ON push button initiates the BITE
test sequence. The push button is lit while BITE is in
progress. The light goes out upon completion of
BITE.
6. The POWER SUPPLY FAIL indicator
illuminates if the power supply-video converter fails
BITE.
7. The POL switch is a two-position switch that
selects the polarity of video signals from the
postamplifiers of the receiver-converter detector array
video amplifier circuits. In the WHT HOT position,
the hot targets appear white on the video indicator. In
the BLK HOT position, the hot targets appear black
on the indicator.
8. The FOV switch selects either wide (WIDE)
or narrow (NAR) field of view. It does this by
switching an afocal lens assembly in or out of the
optical path of the receiver.
9. The GAIN knob adjusts the dc level of the
video output to the video indicator. This affects the
contrast of targets on the indicator.
10. The LEVEL knob adjusts the dc level of the
video output of the receiver-converter. This affects
the brightness of the background on the video
indicator.
11. The RCVR CONV FAIL indicator
illuminates if the receiver-converter fails BITE test.
12. The FOCUS switch is a four position rotary
switch that selects target range for focusing the afocal
lenses in the narrow FOV.
13. The RTCL BRT knob controls the brightness
of the reticle that is superimposed on the video signal
applied to the video indicator.
14. The NOT READY indicator illuminates
when the receiver-converter is not at operating
temperature, when gyro spin-up is not complete, or
when BITE is in the fault isolation mode.
15. The COOLING indicator illuminates to
indicate the IR detectors in the receiver-converter
have not reached operating temperature.
16. The RCVR O TEMP indicator shows
excessive temperature within the receiver-converter.
17. The SERVO FAIL indicator illuminates if the
control servomechanism fails the BITE test.
18. The ELEVATION knob controls the receiver
slew signals (elevation) in the position mode of
operation.
VIDEO INDICATOR
The typical video indicator (fig. 6-18) is an
875-line, 30 frames-per-second, closed-circuit TV
monitor. On the front of the WRA is an ON-OFF
power switch, an elapsed time meter, brightness and
contrast controls, and a status indicator. Operation of
the indicator is similar to that of a TV monitor.
Figure 6-27 is a simplified block diagram of a video
indicator’s signal processing circuits.
Composite video from the video line driver
module of the power supply-video converter is
applied to the video amplifier/sync stripper module.
This module separates the video signals (IR,
RETICLE, GAI, and gray scale) from the sync signals
(blanking, clamping, and sync). The module
amplifies the video signals and provides the video
output to the CRT for display. The contrast control is
also injected in the video amplifier/sync stripper
module. The module also sends the composite sync
signals to the vertical, sync, CRT protect, and
brightness control module.
The video amplifier/sync stripper module
processes the composite sync signal. It provides
vertical and horizontal sync signals to the vertical and
horizontal sweep module. It also provides blanking
and clamping signals to the CRT. The brightness
6-26
