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.
The major components of the intercommunication
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.
A line-pull signal consists of one pull or a series of sharp, distinct
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.
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).
Figure 8.11. Communicating with Line-Pull
Signals.
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Table 8.2. Line-Pull Signals.
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