Figure 7-28.--Intercommunicating unit (LS-433A/SIC).

prevents multiple inputs to the amplifier, which could

B amplifier, place all loudspeaker group control

result in unintelligible transmissions to the remote

switches to channel A. When operating under this

loudspeakers.

condition, with all loudspeaker groups connected to one

amplifier, be careful not to overload the amplifier. Use

The microphone control stations located at the

the OUTPUT TEST switch and meter to test the output

remote stations consist of a flexible microphone and an

of the channel in use. Proper output is indicated when

associated microphone jackbox. These remote stations

the meter fluctuates with peaks occuring about midscale

are connected to the amplifier as separate inputs.

(0 dB).

Loudspeakers

INTERCOMMUNICATION SYSTEMS

Loudspeakers are located in the sonar control area

and at each remote location. Loudspeakers located

Intercommunication (intercom) systems provide

adjacent to control stations are wired so that they are

for two- way transmissions of orders and information

disconnected from the amplifier when the adjacent

between stations. Each intercom unit contains its own

control station is operated.

amplifier.

MAINTENANCE

INTERCOMMUNICATING UNITS

Maintenance of the system consists of routine

LS-433A/SIC AND LS-434A/SIC

preventive maintenance and corrective maintenance.

Maintenance for the two-way system is essentially the

Regardless of their construction, intercommunicat-

same as for the one-way system. Routine preventive

ing units on naval vessels are connected together

maintenance consists of inspecting, cleaning, and

electrically in a system. The electrical characteristics

t e s t i n g . Corrective maintenance consists of

that must be identical to permit interconnection in a

troubleshooting and replacing parts.

system are (1) audio-amplifier input and output

requirements, (2) amplifier output impedance to the

As with the one-way system, operation of this equip-

loudspeaker line transformer, (3) supply voltages and

ment involves the use of high voltages with no interlocks

currents, (4) call and busy signal voltages, and (5)

provided. Therefore, all safety regulations and

interconnection circuits.

precautions must be observed at all times when you are

performing corrective maintenance on this equipment.

One type of intercom unit, the LS-433A/SIC (fig.

7-28), can originate calls up to a maximum of 10 other

Malfunctions can usually be localized by using the

comparison method. A problem common to all

microphone control stations usually indicates a failure

within the circuits of the control rack. A problem

peculiar to only one station indicates the fault could be

located in the control rack the microphone control

station, or the cables connecting the control station to

the control rack.

If the entire system is inoperative, check the

POWER AVAILABLE indicator lamp on the control

rack. If the lamp is not lit, check the switch that provides

power to the control rack. If the lamp is lit, check the

position of the switches on the control panel. If all the

control panel switches are in their proper positions,

check for blown fuses. If there is no indication of a

blown fuse(s), refer to the applicable technical manual

and schematic diagram for the system.

The system's dual channel design, with switching

controls, permits continued operation of the system

when one channel fails. If there is a failure of the channel

A amplifier, place all loudspeaker group control

Figure 7-28.--Intercommunicating unit (LS-433A/SIC).

switches to channel B. If there is a failure of the channel

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