Local Channel Selection

0.l-mc automatic positioner re-

position. While the frequency se-

lays K1201, K1202, and K1203.

lector is running, K601 cannot be

(2) Contacts 3 and 4 of K1204 close.

operated from any position because

relay K1204 (fig. 27) supplies +26.4

This action applies +26.4 volts dc to

volts dc to energize relay K1. Work

tuning motor B1201. The pawl lifts

from the detent wheel associated

relay K1 energizes and opens con-

with B1201, permitting it to run.

tacts 6 and 7 of K1, thereby inter-

rupting the ground return for relay

(3) Motor B1201 drives the channel in-

K601. Relay K1 prevents trans-

dicator wheel, the preset channel

mission whi1e the rt unit is

memory drum, and the local and

channeling from one frequency to

remote switches S1205 and S1206.

another.

Although motor B1201 is physically

(3) When relay K601 operates, con-

connected to the 10-mc, 1.0-mc,

and 0.l-mc detent wheels through a

tacts 5-15 and 3-13 of relay K601

slip-clutch arrangement, these

close. Contacts 5-15 complete the

wheels do not turn at this time be-

26.4 volts dc circuit to relay K602,

cause they are locked by pawls that

antenna relay K101, injection relay

slip into the detent wheels when-

K102, tr relay K401, tr relay K802,

ever the associated relay is deen-

and high-voltage relay K2, Con-

ergized.

tacts 3 and 13 of K601 ground the

(4) Local-seeking switch S1205,

if. avc bus.

ganged to the preset channel mem-

(4) When NOR-BB switch S801 is in the

ory drum, turns until the rotor

BB position and the tr relays are

finds the one position that opens the

energized, contacts 3 and 5 of relay

ground path to terminal 2 of relay

K602 close and supply an encoder

K1204. When S1205 reaches this

keying ground to the broadband en-

position, relay K1204 denergizes

coder from contacts 4 and 5 of NOR-

and drops the pawl into the detent

BB switch S801A.

wheel which prevents further rota-

tion of the preset channel memory

83. Local Channel Selection

drum and the local- and remote-

(fig. 27)

seeking switches S1205, and S1206.

a. Channel Selection Function. Any one

(5) When relay K1204 deenergizes,

of 19 preset channels can be selected from

contacts 3 and 5 of K1204 close and

the front panel of the rt unit by turning

and the +26.4 volts dc supply is

CHAN SEL selector switch S705 to the de-

removed from tuning motor B1201

sired channel. When the CHAN SEL switch

and applied to the coils of the

is turned, terminal 2 of channel selector

10.0-mc, 1.0-mc and 0.1-mc re-

automatic position relay K1204 is

lays K1201, K1202, and K1203.

grounded through contacts 1 and 2 of S705C,

b. Operation of 10-Mc Automatic Posi-

local-seeking switch S1205, and switch

tioner. Assume that the preset frequency

S705B. (In figure 27, local-seeking switch

for channel 19 is 376.3 mc. The left pin

S1205 is shown in the position to which it

(first pin counting from the left (TM 11-

will be advanced after the channel selec-

5820-222-10) of the preset channel mem-

tion sequence ( b below) is completed. Just

ory drum selects the first digit of the

before switch S1205 was advanced to this

preset channel frequency. This pin opens

position, the ground return path for K1204

one of the two normally closed contacts

was through contacts 8 and 5 of S1205 front,

of switch S1210A. The left-center pin (sec-

ond pin from the left) of the preset channel

and 5 and 7 of S705B). When relay K1204 is

energized, the following sequence occurs:

memory drum selects the second digit of

the preset channel frequency. This pin

(1) Contacts 3 and 5 of K1204 open.

opens one of the 10 normally closed con-

This action removes the 26.4 volts

tacts of switch S1210B. These two switches

dc supply from 10.0-, 1.0-, and