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Reference Speed Selection
azimuth. The alpha angle is held constant and grid
heading, rather than true heading, is sent to the ship's
The software program controls the reference
equipment. Otherwise, the equipment's function is the
same as for the AUTO CAL mode.
speed selection function. The REF SP switch
is positioned by the operator to define to the
software program the operational mode required. In
the OVRD LOG position, the REF SP switch
provides a ground via the dimming control circuit
The major functions of the stabilized gyrocompass
are supported by several supporting or subordinate
card to energize the OVRD LOG indicator. The
functions. The supporting functions are described in the
REF SP OFF indicator is controlled by the pro-
following paragraphs.
The ship's EM log input is changed from synchro
Latitude Set
format to sine and cosine values by the Scott "T"
transformers in the A/D multiplexer transformer. The
The entry of latitude data maybe made during the
EM log sine and cosine signals are selected by the
leveling sequence (except during the north and south
A/D multiplexer and converted to a tangent value, in
gyrocompassing phases) and at anytime the system is
digital format, by the A/D converter. The EM log tangent
NAV ready. The gyrocompass is ready to receive a
latitude entry when the ENTER LAT switch indicator
signal is then applied to the processor. When the
(fig. 4-44) is on. The software program commands
REF SP switch is set to OFF, the processor ignores the
the ENTER LAT switch indicator on when power
EM log inputs and the gyro operates in the free-
is applied and when the position of the MODE switch
inertial state. When the REF SP switch is set to EM
is changed. If the ENTER LAT switch-indicator is not
LOG, the processor tells the software program to
on, entry can be accomplished by pressing the
implement gyro operation, damped by the EM log
ENTER LAT switch indicator ONCE. The gyro
compass will then be able to receive a latitude entry for
velocity information.
1 minute.
The EM log velocity information is monitored for
With the DSPL SEL switch set to LAT and the
reasonableness by the software program. When it
ENTER LAT switch indicator on (fig. 4-44), latitude
determines that the velocity information does not
entry is made by setting the desired latitude
meet the reasonableness test, the processor will
(hemisphere, degrees, and minutes) with the
command the equipment to ignore the velocitly data and
thumbwheel switch, then pressing and releasing the
ENTER LAT switch indicator. The ENTER LAT switch
operate in the free-inertial state. The processor will also
indicator will go off and the selected latitude will be
initiate a reference speed off signal, causing the REF SP,
displayed on the digital display.
OFF indicator to light. The operator can override the
reason- ableness test by setting the REF SP switch to
Data Display
OVRD LOG. In the OVRD LOG position, the processor
disables the velocity monitor and commands the
software program to use the EM log velocity
Several pieces of data are available for display on
the control indicator panel. The data available for
information for damping purposes. The REF SP, OFF
display is latitude, electromagnetic (EM) log, ship's
indicator will go off, and the OVRD LOG indicator will
heading, pitch, roll, and test (table 4-3). The desired data
come on, indicating the equipment is operating in a
is displayed by setting the DSPL SEL switch to the
damped state.
appropriate position. Also, under software control, but
not selectable, are the MODE, ALIGN indicator, and the
When the REF SP switch is set to DOCK, the
MODE, NAV indicator. When the alignment sequence
processor tells the software program to use a zero
is complete, the software program turns the MODE,
reference velocity for damping instead of the EM log
NAV indicator on, and the MODE, ALIGN indicator
velocity input.

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