Section II. OPERATION UNDER USUAL CONDITIONS

TM 11-6625-542-14-1

Table 3-1. Operator Controls and Indicators-Continued

Control or indicator

Function

CRYSTAL 'EATER lamp

When illuminated, indicates crystal oscillator oven is functioning

and

is in a heat cycle.

NOTE

This lamp operates independently of POWER ON switch, and

will

illuminate immediately when power is applied to AN/USM-

108A, and will continue to function regardless of position of POWER

ON switch.

Section II. OPERATION UNDER USUAL CONDITIONS

connector. Any combination of the 14 buttons may be

3-3. Starting Procedures

depressed to obtain time-marks equal to the arithmetic

a. Refer to paragraph 2-3 for cable connections.

total of the values depressed.

b. Refer to paragraph 2-4 and connect to proper

(3) Time-marks (jacks):

ac power source.

Insert a connector into the jacks to permit individual

c. Press CANCEL pushbutton.

usage of a particular time-mark, independent of what

d. Set POWER ON switch to ON.

pushbuttons are depressed. Any or all of the jacks may

e. Select proper cable for obtaining signal

be utilized at a given time.

desired.

(4) TRIGGER RATE (pushbuttons): Depress

Depress pushbutton, or select jack, that will

any one of the six TRIGGER RATE pushbuttons to

provide desired signals as follows:

provide a trigger pulse at the TRIGGER OUT connector.

(1) SINE WAVE (pushbuttons): Depress one

Only one push-button may be depressed at one time.

of the three sine wave push-buttons to provide a sine

3-4. Stopping Procedures

wave signal of that frequency at the MARKER OUT

connector.

a. Remove all cables and connectors.

(2) Time-marks (pushbuttons): Depress any

b. Depress CANCEL pushbutton.

one of the 14 time-mark push-buttons to provide a time-

c. Set POWER ON switch to off.

mark, at the rate selected, at the MARKER OUT

Section III. OPERATION UNDER UNUSUAL CONDITIONS

In tropical climates, electronic equipment may be

3-5. Operation in Arctic Climates

installed in tents, huts or, when necessary, in

Subzero temperatures and climatic conditions associated

underground dugouts. When equipment is installed

with cold weather may hamper the efficient operation of

below ground, and when it is set up in swamp areas,

electronic equipment. Instructions and precautions for

danger of moisture damage is more acute than normal in

operation under such adverse conditions follow:

the tropics. Ventilation is usually very poor, and the high

a. Keep the equipment warm and dry. If the

relative humidity causes condensation on the equipment

equipment is not kept in a heated enclosure, construct

whenever its temperature becomes lower than the

an insulated box for its protection.

ambient air. To counteract this condition, place lighted

b. Make certain the equipment has been warmed

electric bulbs under the equipment.

up sufficiently before use. This may take from 15 to 30

3-7. Operation in Desert Climates

minutes, depending on the temperature of the

surrounding air.

The main problem with electronic equipment in desert

c. When equipment which has been exposed to

areas is the large amount of sand and dust that lodges in

the cold is brought into a warm room, it will sweat until it

the moving parts and mechanical assemblies. Cleaning

reaches room temperature. When the equipment has

and servicing intervals should be shortened according to

reached room temperature, dry it thoroughly.

local conditions.

3-6. Operation in Tropical Climates

3-3