TM 11-5840-281-35/1
Figure 2-18. Unblanking and az-el relay trigger circuit, simplified schematic diagram
out-of-three counter circuit initiated by the simultaneous
and its collector goes toward +20 volts. This occurs in
trigger and the simultaneous reset trigger from the
each elevation scan sector, whether it is going into an
simultaneous operation cam on Antenna AS-1291/TPN-
up-scan or down-scan. After Antenna AS-1291/TPN-8
8. This cam lobe is set at approximately 17 degrees and
has scanned through its 11-degree sector, the
extends over each extreme of the 10-degree cam. Each
simultaneous reset trigger turns transistor Q4002 off and
time the microswitch rolls onto the cam, it produces a
its collector goes toward ground; therefore, relay K4014
simultaneous trigger (fig. 2-18). Each time it rolls off the
cannot be operated except during an elevation up or
cam, it produces a simultaneous reset trigger. These
downscan. The simultaneous reset trigger is also
two triggers operate the counter circuit composed of
coupled to bistable multivibrator transistors Q4007 and
transistors Q4001, Q4002, Q4005, Q4006, Q4007, and
Q4008 each time transistor Q4006 conducts, and
Q4008 in Remote Switching Control C-6989/TPN-18.
transistor Q4007 couples a positive trigger back to
(c) The counter, through inverter amplifier
transistor Q4005 and Q4006 through diode CR4009 (if
transistor Q4003, operates relay switching transistor
Q4006 is conducting).
Q4004, which operates relay K4014.
(e) The simultaneous elevation trigger (fig. 2-17)
Relay K4014 is operated when transistor Q4004
is coupled through switch S1003 on Antenna Drive TG-
conducts. Transistor Q4004 conducts when transistor
113/TPN-8. This switch is adjusted to open the trigger
Q4003 is turned on. The base of transistor Q4003
line when Antenna AS-1292/TPN-8 is about 80 degrees
requires a voltage in excess of +4.5 volts to turn it on;
ahead of the center of precision azimuth sector, and
thus, relay K4014 cannot be operated (unless in SIMULT
closes about 20 degrees after center; thus, no triggers
operation) since the base of transistor Q4003 is
can get through to produce an AND gate during this time.
grounded when relay K4008 is not operated. In SIMULT
(f)The first line (fig. 2-19) shows the ppi sector
operation, transistor Q4003 is turned on by a diode AND
where triggers are locked out, and the arrows represent
logic circuit consisting of CR4003 and CR4004.
the direction of the ppi trace at the time each trigger is
The collector of transistor Q4002 and the collector of
produced. The solid portion of the baseline of line (a)
transistor Q4008 must be at a positive potential to turn
indicates the closed trigger line, and the dashed portion
on transistor Q4003.
indicates the time that the triggers are locked out. Since
(d) In the counter circuit, transistor Q4002 is
transistor Q4005 must conduct if transistor Q4007 is
turned on by the simultaneous trigger
2-31
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