Diver Communications

The surface-supplied diver has two means of communicating with the surface, depending on the type of equipment used. If the diver is using the MK 21 MOD 1, or the MK 20 MOD 0, both voice communications and line-pull signals are available. Voice communications are used as the primary means of communication. Line-pull signals are used only as a backup. Diver-to-diver communications are available through topside intercom, diver-to-diver hand signals or slate boards.

8-7.1 Diver Intercommunication Systems. The major components of the intercommu nication system include the diver's earphones and microphone, the communication cable to each diver, the surface control unit, and the tender's speaker and microphone. The system is equipped with an external power cord and can accept 115 VAC or 12 VDC. The internal battery is used for backup power requirements. It should not be used as the primary power source unless an external power source is not available.

The intercom system is operated by a designated phone talker at the diving station. The phone talker monitors voice communications and keeps an accurate log of significant messages. All persons using the intercom system should lower the pitch of their voices and speak slowly and distinctly. The conversation should be kept brief and simple, using standard diving terminology. Divers must repeat verbatim all directions and orders received from topside.

The approved Navy diver communication system is compatible with the MK 21 MOD 1 and the MK 20 MOD 0. This is a surface/underwater system that allows conference communications between the tender and up to three divers. It incorporates voice correction circuitry that compensates for the distortion caused by divers speaking in a helium-oxygen atmosphere.

The divers' voices are continuously monitored on the surface. All communications controls are located at the surface. The topside supervisor speaks with any or all of the divers by exercising the controls on the front panel. It is necessary for a phone talker to monitor and control the underwater communications system at all times.

8-7.2 Line-Pull Signals. A line-pull signal consists of one pull or a series of sharp, dis tinct pulls on the umbilical that are strong enough to be felt by the diver (Figure 8-11). All slack must be taken out of the umbilical before the signal is given.

The line-pull signal code (Table 8-2) has been established through many years of experience. Standard signals are applicable to all diving operations; special signals may be arranged between the divers and Diving Supervisor to meet particular mission requirements. Most signals are acknowledged as soon as they are received. This acknowledgment consists of replying with the same signal. If a signal is not properly returned by the diver, the surface signal is sent again. A continued absence of confirmation is assumed to mean one of three things: the line has become fouled, there is too much slack in the line, or the diver is in trouble.

If communications are lost, the Diving Supervisor must be notified immediately and steps taken to identify the problem. The situation is treated as an emergency (see paragraph 6-12.5.3.2).

There are three line-pull signals that are not answered immediately. Two of these, from diver to tender, are "Haul me up" and "Haul me up immediately." Acknowledgment consists of initiation of the action. The other signal, from the tender to diver, is "Come up." This signal is not acknowledged until the diver is ready to leave the bottom. If for some reason the diver cannot respond to the order, the diver must communicate the reason via the voice intercom system or through the line-pull signal meaning "I understand," followed (if necessary) by an appropriate emergency signal.

Figure 8-11. Communicating with Line-Pull Signals.

Table 8-2. Line-Pull Signals.

From Tender to Diver

Searching Signals (Without Circling Line)

1 Pull

"Are you all right?" When diver is descending, one pull means "Stop."

7 Pulls

"Go on (or off) searching signals."

2 Pulls

"Going Down." During ascent, two pulls mean "You have come up too far; go back down until we stop you."

1 Pull

"Stop and search where you are."

3 Pulls

"Stand by to come up."

2 Pulls

"Move directly away from the tender if given slack; move toward the tender if strain is taken on the life line."

4 Pulls

"Come up."

3 Pulls

"Face your umbilical, take a strain, move right."

2-1 Pulls

"I understand" or "Talk to me."

4 Pulls

"Face your umbilical, take a strain, move left."

3-2 Pulls

"Ventilate."

4-3 Pulls

"Circulate."

From Diver to Tender

Searching Signals (With Circling Line)

1 Pull

"I am all right." When descending, one pull means "Stop" or "I am on the bottom."

7 Pulls

Same

2 Pulls

"Lower" or "Give me slack."

1 Pull

Same

3 Pulls

"Take up my slack."

2 Pulls

"Move away from the weight."

4 Pulls

"Haul me up."

3 Pulls

"Face the weight and go right."

2-1 Pulls

"I understand" or "Talk to me."

4 Pulls

"Face the weight and go left."

3-2 Pulls

"More air."

4-3 Pulls

"Less air."

Special Signals From the Diver

Emergency Signals From the Diver

1-2-3 Pulls

"Send me a square mark."

2-2-2 Pulls

"I am fouled and need the assistance of another diver."

5 Pulls

"Send me a line."

3-3-3 Pulls

"I am fouled but can clear myself."

2-1-2 Pulls

"Send me a slate."

4-4-4 Pulls

"Haul me up immediately."

ALL EMERGENCY SIGNALS SHALL BE ANSWERED AS GIVEN EXCEPT 4-4-4

A special group of searching signals is used by the tender to direct a diver in moving along the bottom. These signals are duplicates of standard line-pull signals, but their use is indicated by an initial seven-pull signal to the diver that instructs the diver to interpret succeeding signals as searching signals. When the tender wants to revert to standard signals, another seven-pull signal is sent to the diver which means searching signals are no longer in use. Only the tender uses searching signals; all signals initiated by the diver are standard signals. To be properly oriented for using searching signals, the diver must face the line (either the lifeline or the descent line, if a circling line is being employed).

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