Section III
Paragraphs 3-12 to 3-13
in such a way as to make the 30 cps output voltage
is derived from a bridge circuit connected to one of
constant for all switch positions. C-1415 and R-1449
the secondaries of T-1401. See figure 3-8. The two
comprise the zeroing adjustment for the variable phase
signals are fed through isolation resistors R-1419 and
signal allowing the VOR zero of the complete instru-
R-1468 and applied simultaneously to the grid of ampli -
ment to be varied over a narrow range for calibration
fier V-408B. The bridge circuit is adjusted with the
purposes.
LOC CENTER control so that no 30 cps voltage
will be applied to the grid of V-1408B when the LOC -
GS control is set in the middle of the white center
volt dynamotor furnishing unregulated B+ and three
sector on the panel. This simulates an on-course
sources of regulated B+ in conjunction with regulator
signal. As the LOC -GS potentiometer is turned off
tubes V-141O, V-1411, and V-1412. See figure 3-7.
center, a 30 cps signal in-phase with the 30 cps refer-
The three separate regulated voltages are required to
ence phase signal or 180 degrees out-of-phase with it
keep the audio levels constant and to prevent B+ inter -
will appear on the grid of V-1408B, depending upon
action.
the direction of rotation. The amplitude of this 30 cps
signal depends on how far off center the LOC -GS po-
tentiometer is set. With the potentiometer set on the
ation requires a 9960 cps FM signal and a 30 cps
top line of either the right or left segment this 30 cps
signal of reversible phase. The 9960 cps signal is
signal should modulate the r-f carrier 11.5%; on the
supplied by the 9960 cps FM oscillator described in
15
