Controls and Indicators

calls will be heard in the handset and the reproducer

stations. Another type of intercom unit, the

simultaneously.

LS-434A/SIC, can originate calls up to a maximum of

20 other stations. There is, however, no operational

A portable microphone can also be used with this

difference between these two types of units.

equipment. The operation is the same, except the push

button on the portable microphone is used instead of the

Reproducer

normal talk switch.

VOLUME CONTROL.-- The volume control is

The reproducer serves a dual function. When it is

associated with a variable impedance transformer inside

the transmitting station, it performs as a microphone;

the unit. As the knob is rotated, the electrical energy

when it is the receiving station, it performs as a normal

passing through the transformer to the loudspeaker is

speaker; amplification occurs in the calling unit.

increased and the volume or sound output of the

loudspeaker increases correspondingly. The volume

Controls and Indicators

control has no effect on the volume of the signal

transmitted from the amplifier; thus, each unit in the

The controls consist of the push-button assembly,

system can control the incoming volume to the desired

talk switch, volume control, and dimmer control. The

level.

indicators consist of the busy light, call light, release

DIMMER CONTROL.-- The dimmer control

light, and station designation lights.

controls all illumination of the unit. The signal lights

PUSH-BUTTON ASSEMBLY.-- The push-

(release, busy, and call) are off when the control knob is

in the extreme counterclockwise position and are fully

button assembly, or station selector switches, are located

lighted for all other positions. The station designation

at the top of the front panel. The locations of the various

lights are lighted for all positions of the control knob,

units associated with the push button is engraved on the

station designation plate immediately below the push

and illumination increases as the knob is turned

button. When the button is depressed, it will lock into

clockwise.

the operated position until the release push button is

RELEASE LIGHT.-- The release light is located

depressed to return them to the nonoperated position.

under the release push button. When the release push

button is in the depressed, or operated, position, the light

The 10-station unit (LS-433A/SIC) is provided with

will be out. When the release push button is in the

one bank of 10 selector switches. The 20-station unit

nonoperated position, the light will be on.

(LS-434A/SIC) is provided with two banks of 10

selector switches each. During standby periods, the

BUSY LIGHT.-- The busy light is lighted when a

release push button is kept in the depressed, or operated,

station selector switch is depressed and the station being

position. When any station selector switch is depressed,

called is busy. When the busy light is lighted, depress

the release push button is restored to the nonoperated

the release push button and restore the station selector

position and the release lamp under the push button will

switch and call later.

be lighted. At the conclusion of the conversation, the

CALL LIGHT.-- The call light is lighted when a

release push button should again be depressed, restoring

station is being called by another station. The call light

the station selector switches to the nonoperated position

will remain lighted until the calling station releases the

and extinguishing the release lamp.

called station's push button.

TALK SWITCH.-- The talk switch serves to select

DESIGNATION LIGHTS.-- The designation

the function of the reproducer. When the switch is

lights are located at each end of the station designation

depressed, the reproducer functions as a microphone

plate. These lights remain lighted at all times and

and couples the reproducer (microphone) signal to the

illuminate the various stations engraved on the

amplifier and from the amplifier to the receiving station.

designation plate.

When the spring-loaded talk switch is released, the

reproducer functions as a loudspeaker and is ready to

Amplifier

receive information.

The amplifier is a three-stage, push-pull amplifier

A handset can be used with the intercom unit in

that uses transformer input and output coupling. The

place of the reproducer. The operation is the same,

amplifier uses an internal ac power supply provided by

except that the push button on the handset is used as the

an unregulated dual diode. The primary advantages

talk switch in place of the normal talk switch. Incoming

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