TM 11-5840-281-35/1
and the base of transistor Q2001. The negative 400-pps
adjustment of the az angle voltage and the el angle
trigger at the base of transistor Q2001 will cause Q2001
voltage applied to emitter-follower transistor Q2101.
to begin conducting and go into saturation. The 1200-
(b) The vertical precision control
pps trigger coincident with the 400-pps trigger will be
circuits from Pulse Generator O-1333/TPN-18 are used
bypassed to ground through transistor Q2001 and diode
to center the precision display vertically and are applied
CR2038. The SCAN MODE switch S1102 on the left-
to emitter-follower transistor Q2105 of the fixed coil
hand Control-Indicator C-6988/TPN-18 must be placed
amplifier. The signals from transistors Q2101 and
to the SEARCH position (or the SCAN MODE switch
Q2105 are applied to differential amplifier transistors
S1102 on the display containing the mixer amplifier
Q2102 and Q2106 where the az-el angle voltage is
under consideration must be placed to the IFF position)
referenced to a level determined by the dc vertical
to provide transistor Q2001 with the supply voltage of -28
centering voltage input to transistor Q2105. The dc
volts. (IF SCAN MODE switch S1102 of the left-hand
vertical centering voltage is derived from the precision
Control-Indicator C-6988/TPN-18 is placed to SIMULT
vertical centering control. The current through the
position, the -28 volt supply will be connected to the
deflection coils varies in accordance with the az-el angle
circuitry of transistor Q2001 in the right-hand display.)
voltage and produces the vertical movement of the time-
(2) If the -28 volts is present, the 1200-pps
base sweep; therefore, the vertical movement of the
triggers are present at the collector of transistor Q2001,
time-base sweep is synchronized with the scan of the
and the 400-pps triggers are present at the base of
transistor Q2001, each 400-pps trigger will occur
c. Mixer-Amplifier Circuit (fig. 7-14 and 7-48).
simultaneously with one of the 1200pps triggers. The
The mixer-amplifier applies the intensity gate to the grid
negative 400-pps trigger at the base will turn on
of the crt. The touchdown marker, range marks, radar
transistor Q2001 and its collector will be near ground
video, iff video, and cursor pulse are mixed, amplified,
potential.
The coincident 1200-pps trigger at the
and applied to the cathode of the crt.
collector of transistor Q2001 will be shunted out through
Q2001. Diode CR2001 will be back-biased and the
1200-pps trigger cannot be fed to transistor Q2003 side
NOTE
of the flip-flop. The 400-pps trigger is routed to the
transistor Q2002 side of the flip-flop causing Q2002 to
When Radar Set AN/TPN-18 is used
conduct and cutting off transistor Q2003. With transistor
with switching capability in a landing
Q2003 cut off, its collector goes to -12 volts, producing a
control center system, master operation
negative gate from 0 to -12 volts. This negative gate is
of either Control-Indicator C-6988/ TPN-
applied to the base of gate amplifier transistor Q2004,
18 can be selected, with the second
cutting off Q2004 and causing its collector to produce a
display assuming slave operation.
positive gate from -12 to +12 volts. This positive gate will
back-bias diode CR2014 and cut off gate amplifier
(1) The input triggers to the mixer amplifier
transistor Q2005. The collector of transistor Q2005 will
are the 1200-pps radar trigger and the 400-pps iff trigger.
go from +12 to -12 volts, producing a negative gate
When RANGE MILES switch S1101 is placed to 5-, 10-,
which will back-bias diode CR2015.
20-, or 40-mile range position, and SCAN MODE switch
With diodes CR2014 and CR2015 back-biased, diodes
S1102 on master Control-Indicator C-6988/TPN-18 is
CR2010 through CR2013 will conduct, allowing iff video
placed to SEARCH position, the 1200and 400-pps
to be applied to the base of amplifier transistor Q2006.
triggers are applied to the collector and base,
IFF VIDEO control R2001 is used to adjust the level of
respectively, of inhibitor transistor Q2001. If master
the iff video applied to the base of transistor Q2006.
Control-Indicator C-6988/TPN-18 SCAN MODE switch
Range marks and radar video are mixed with the iff video
S1102 is placed to SIMULT position, both the 1200and
at the base of transistor Q2006, amplified by Q2006, and
400-pps triggers are applied to transistor Q2001 in slave
applied to the cathode of the crt.
Control-Indicator C-6988/ TPN-18 mixer amplifer only.
(3) When no 400-pps trigger is applied to
When RANGE MILES switch S11OI on either Control-
the base of transistor Q2001 (in precision display mode),
Indicator C-6988/TPN-18 is placed to the 80-mile range,
Q2001 will be cut off and the 1200-pps (or
the 400-lups trigger will be applied to both the collector
2-49
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