Section IV
signal are fed to AUDIO SELECTOR switch section
4-65. The distorted signal is
fed through Z1401 and
S1402B and each signal will modulate the r-f carrier
Z1403, which pass only the third (90 cps) and fifth
40 percent. When the LOC-GS control is set to the
(150 cps) harmonics, respectively. The 90-cps sig-
top line on the left segment, the 90-cps level till fall
nal is then fed to cathode-coupled limiter V1405 and
as the 150-cps level rises until the 150-cps signal is
the 150-cps signal is fed to cathode-coupled limiter
3.0 db higher than the 90-cps signal. If the LOC-GS
V1404. AUDIO SELECTOR switch section S1402C
control is set to the bottom line on the left segment
disables the 30-cps variable phase signal on LOC,
there is a 3.75 db difference between signals. When
TONE LOC, GLIDE SLOPE, 1000~ and 9960 FM by
the LOC-GS is set to the right segment, the signals
grounding the output of V1401A. On 90~, S1402C
are reversed and the 90-cps level becomes greater
grounds the grid of V1404 disabling the 150 cps cir-
than the 150-cps level.
cuit. On 150~, S1402C grounds the 90 cps signal at
the grid of V1405.
4-68. For TONE LOC operation, the 90-cps and 150-
4-66. Limiters V1405 and V1404 keep the 90- and
cps are fed through dropping resistors R1438 and
150-cps signals at \equal and constant amplitudes.
R1437 and AUDIO SELECTOR switch sections S1402F
90~ LEVEL control R1432 and 150~ LEVEL control
R1431 in the V1405 and V1404 cathode circuits control
front and S1402F rear to LOC-GS attenuator R1416A.
the output level of the limiters. Further filtering is
The 90-cps and 150-cps levels at its midposition are
provided by Z1402 and Z1404 and 90-cps and 150-cps
still equal, but when the control is set to the top line
signals of constant amplitude appear across R1436
of the right or left segment there is a 6.0 db differ-
and R1435, respectively.
ence in signal levels. At the bottom line of either
segment the level difference is now 7.5 db. Since
4-67. For GLIDE SLOPE operation, the 90-cps and
only 20% modulation is required for each tone for an
150-cps signals are fed through dropping resistors
on-course signal in TONE LOC, the output of the at-
R1492 and R1493 and AUDIO SELECTOR switch sec-
tenuator is reduced by voltage divider R1442, R1566
and R1443. On 90~ and 150~ AUDIO SELECTOR
tions S1402F front and S1402F rear to LOC-GS at-
switch sections S1402A front and S1402D front are
tenuator R1418A. When the LOC-GS is set to its mid-
position (middle of the white center segment on the
used and the output is also taken from the voltage
front panel), equal amounts of 90-cps and 150-cps
divider.