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tacts 2 and 3 of S705C are closed by a cam,
B1201 through closed contacts 3
and 4 of relay K1202. The relay
and contacts 1 and 2 of S705C are opened.
also lifts the pawl from the detent
Thus, control of the frequency selector
wheel, which allows the tuning mo-
system is transferred from the CHAN SEL
tor to drive the l.0-mc automatic
selector switch on the front panel to the
CHANNEL selector switch, S1503, located
positioner through a slip clutch.
The l.0-mc seeking switch, S1203,
on Radio Set Control C-1439/U.
ganged to the 1.0-mc automatic po-
b. The ground circuit to channel selector
sitioner, rotates until the detent
automatic positioner relay K1204 is com-
reaches position 6. The ground cir-
pleted through contacts 6 and 8 of remote-
cuit to relay K1202 is then opened,
seeking switch S1206 and contacts 6 and 7
and the relay deenergizes and
of CHANNEL selector switch S1503 front.
drops the pawl into the detent wheel,
This causes tuning motor B1201 to drive
which prevents further rotation of
the preset channel memory drum and
the indicator, detent wheels, and
remote-seeking switch S1206 until there-
the l.0-mc seeking switch.
mote-seeking switch reaches the channel
(3) If the 1.0-mc seeking switch has
position selected by the CHANNEL switch
previously been set to a position
that opens the ground circuit to relay
lower than 6, it rotates counter-
K1204. Channel frequency selection is ac-
clockwise through positions 0 and
complished from the remote position in the
9 to reach position 6. At this in-
same manner as described for local chan-
stant, the detent on the rear wafer
nel selection (para 83).
of S1203 momentarily grounds the
10.0-mc automatic positioner re-
lay K1201 through switch contact
85. Manual Frequency Selection
B of S1203 rear. This allows time
for the 10.0-mc automatic posi-
When CHAN SEL switch S705 is turned
tioner to recycle to tune the uhf
to the MANUAL position, any one of the
tuning elements to the higher fre-
1,750 channel frequencies can be selected
quency setting:
by physically positioning the MANUAL
d. Operation of 0.1-MC Positions. The
right pin of the preset channel memory
controls S706, S707, and S708.
drum closes one of the 10 normally open
contacts of switch S1210D to control the
a. When S705 is turned to MANUAL, the
selection of the fourth digit of the preset
preset channel memory drum rotates to
channel frequency. Selection of this digit
position M. In this position, a nylon bar
is similar to the selection of the third
opens all contacts on switches S1210A
digit ( c above).
and S1210B (fig. 27). Switch contacts on
switches S1210C and S1210D are normally
Note. Once the preset chanel memory drum
open (fig. 27). Switch S705A is operated
reaches the selected channel and the +26.4 volts
is supplied to the 10.0-, the 1.0-, and the 0.1-mc
by a cam to connect TENS switch S706 to
automatic positioner relays K1201, K1202, and
10.0-mc seeking switch S1201 in place of
K1203, selection of the individual digits of the pre-
switches S1210A and S1210B. The wafers
set channel occurs simultaneously. Tuning motor
of the TENS, UNITS and TENTHS switches,
B1201 drives the automatic positioner systems
S706, S707 and S708, are grounded through
through slip clutches that permit the motor to run
switch contacts S705A-20, -21, -24, and
when any or all of the automatic positioners are at
Note. Figure 28 shows only the wiring required
84. Remote Channel Selection
to manually select frequencies of 220.0, 238.6,
320.0 and 338.6 mc. The controls and switches
are shown in the 220.0-mc position. For this ex-
a. When CHAN SEL selector switch S705
ample, assume that the MANUAL FREQUENCY
is on the REMOTE PRESET position, con-
controls are changed from 220.0 mc to 238.6 mc.

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