Figure 5-11.--Simplified sound-powered telephone headset-chestset schematic.

noise-attenuating shells consisting of plastic caps lined

Figure 5-11 is a wiring diagram of a type H-200/U

with sound-absorbing material.

sound-powered telephone headset-chestset. Closing the

press-to-talk switch, S1, connects the sound-powered

SOUND-POWERED UNITS.-- The sound-

transmitter unit across the line. The receiver units are

powered transmitter and receiver units used in

permanently connected across the line when the set is

sound-powered telephone headset-chestsets are not

plugged in.

interchangeable. The units differ physically; however,

the principle of operation is the same for both.

Capacitor C1 is in the circuit to prevent the flow of

direct current through the receiver units when the set is

Sound-powered telephone headset-chestset

used on the output side of a sound-powered telephone

receiver units will transmit as well as receive. In the

amplifier. When the set is used on the output side of the

event the transmitter becomes defective, and the set

amplifier, a small dc voltage is placed across the set to

cannot be repaired at once, communication can still be

form an amplifier squelching circuit to avoid acoustical

maintained. Remove either one of the receiving units

feedback when the local set is transmitting. When the

from the headband and use it as a transmitter. Since the

press-to-talk switch, S1, is depressed, direct current

receivers are connected in parallel, either one can be

flows through the transmitter unit, causing a relay in the

used as the transmitter.

amplifier to operate and activate the squelching circuit.

HANDLING HEADSET-CHESTSETS.--

Sound-powered telephone headset-chestsets should be

Capacitor C2 provides for power-factor correction

handled with care so they will be working properly in

and improves the acoustical quality of the set.

the event of an emergency. When not in use they should

The H-200/U can also be modified to meet security

be correctly made up and stowed in their proper place.

requirements for use in the ship's communication center.

The sets are made as waterproof as possible, but

The headset-chestset cord must contain not less than two

they should not be exposed unnecessarily to the weather.

conductors in a single shield.

The cords should not be dragged over sharp edges,

pulled too hard, or allowed to kink. When unplugging

There are two other types of headset-chestsets used

the cord from a jack, always pull on the body of the plug

with the sound-powered telephone system. They are the

and never on the cord. If it becomes necessary to remove

H-201/U and the H-202/U.

the set from the talker's head, hang the set by the head-

The H-201/U is designed for use by plotters and

band and neck strap, and never by the connecting wires.

console operators. This set features a transmitter

DONNING HEADSET-CHESTSETS.-- When

suspended from the headband on an adjustable boom.

donning the headset-chestset, you should use the

The normally open, spring-loaded, press-to-talk switch,

following procedure:

S1, is in a junction box clipped to the talker's belt.

1. Remove the set from the stowage hook or

The H-202/U is a specially designed set for use in

stowage box.

high noise level areas. The receiver units are housed in

2. Hold the set and coiled cord in one hand.

3. Unhook the neck strap and unwind the coiled

cord. Do not allow the set to dangle by its connecting

wires; this could cause open leads.

4. Put the neck strap around the neck and secure it

to the chestplate.

5. Put on the receivers and adjust the ear cushions

for maximum comfort and exclusion of noise.

6. Straighten out any kinks in the connecting wires.

7. Test the headset for satisfactory operation by

blowing into the transmitter with S1 depressed. A

hissing noise should be heard in both receivers.

Figure 5-11.--Simplified sound-powered telephone

8. Remove the jack cover and connect the plug to

headset-chestset schematic.

the jack.

5-13