TM 55-1930-209-14&P-17
h.
When receiving a message, adjust volume control to desired listening level.
i.
To transmit, push PUSH-TO-TALK (PTT) button on microphone and hold it down while giving message. Hold
microphone about 1 inch from your mouth and speak slowly and distinctly, directly into microphone. When
finished, release PTT switch to receive incoming message. Transceiver can not receive incoming message while
transmitting; wait until incoming message is complete before depressing PTT switch.
2-13.2 Depthfinder operations. The Aqua Probe Model 550 digital depthfinder (Figure 2-7) operates like a computer
that is programmed to filter and interpret return signals from sea bottom. It is set and operated according to the
following paragraphs:
a.
Make sure power cable and transducer cables are firmly installed in bottom of depthfinder unit.
b.
Preset the digital depthfinder.
(1)
Turn the power switch (Light-OFF-ON) (Figure 2-6) to center, OFF position.
(2)
All other switches must be in the down position.
(3)
Set SENSITIVITY and SHALLOW alarm knobs to minimum settings.
(4)
Set DEEP alarm knob to maximum setting.
c.
Turn power on by turning toggle switch to: (1) ON (down position) for daylight operations (2) LIGHT (up position)
for night operations
This activates the liquid crystal display (LCD) with an Aqua Meter logo appearing on the left side of the
display. (For night operations the LCD is illuminated with a soft red glow.) The words NO ECHO will appear in the lower
left corner of the LCD at zero sensitivity.
NOTE
If the workboat is over a very hard-packed sandy or rock bottom in shallow water,
the depthfinder may, at zero sensitivity setting, receive enough return signals to
provide a depth reading.
d.
Set SENSITIVITY control for normal depth readings.
(1)
Advance the control knob to that point where water depth just starts to be displayed and the NO ECHO
reading disappears. This is called the sensitivity threshold point.
(2)
From the threshold point, advance the SENSITIVITY control knob two graduations higher than the threshold
point.
(3)
Periodically repeat step (1) and (2) to assure that the two-graduations-above-threshold setting is being
maintained. Significant changes in bottom condition, depth, and sub-surface interference, among other
factors, can affect the echo return strength.
CAUTION
Depth range will not register shallower depths than the range selected but can
register deeper depth.
e.
Select DEPTH range by setting range-finding switch at 2 ft 99 ft (shallow range).
f.
Set UPDATE RATE front panel switch down to FAST to display new LCD readouts approximately twice each
second. The FAST update rate is used both for normal shallow water operations and when navigating in
dangerous areas. The SLOW update rate is used when cruising in known areas or rough water.
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