NORTHROP GRUMMAN NAVITWIN IV, Руководство по эксплуатации, установке и обслуживанию

Страница: 15 / 164

NAVITWIN IV 056360/E
Design and Main Features 1-3
may be entered manually.
• Magnetic compass heading source
In conjunction with a Sperry Marine fluxgate sensor type 4863, fitted
to a compatible magnetic compass, NAVITWIN IV senses the ves-
sel‘s magnetic compass heading and converts it to the NMEA 0183
(IEC 61162) format, including automatic correction for magnetic vari-
ation and sensor calibration values.
• Central gyrocompass control unit
In single, dual and triple gyrocompass systems comprising current
models from the NAVIGAT gyrocompass line, the NAVITWIN IV acts
as the system‘s central control and display unit.
System-wide operational settings are entered at the NAVITWIN IV
and transmitted to the connected compasses. In turn, alarm mes-
sages from the gyrocompasses are indicated and may be acknowl-
edged at the NAVITWIN IV.
• Heading source for Grounding Avoidance Systems
The NAVITWIN IV may form part of a grounding avoidance system
(GAS) according to DNV.
In case of failure of the active heading source, substitute heading
data is automatically provided to the GAS by smoothly changing
over from the last known heading of the active source to the current
heading of a secondary (none-active) source.
Switch-Over Unit, Type 4932
The Switch-Over Unit (SOU), type 4932, is a passive data distribution
unit, which is able to switch a large number of data and signal outputs
from one source to another.
Through control signals from the NAVITWIN IV, the SOU may be put in
either one of three source selection modes:
G1:
Connects the outputs to the inputs from source “G1”.
G2: Connects the outputs to the inputs from source “G2”.
M:
Connects the repeater and sensor data outputs to the data input
from the NAVITWIN IV.
In case of failure of the gyrocompass(es), magnetic compass head-
ing data is available at these outputs as an emergency heading refer-
ence for repeaters and other external equipment.
All other outputs are connected to the corresponding inputs from
source “G1”.
The SOU uses electro-mechanical relays for switching signal and data
lines. As the unit is designed to be used in conjunction with Sperry
Marine‘s NAVIGAT gyrocompasses, the designations of the in- and out-
puts largely correspond to those of the outputs at the NAVIGAT X MK 1,
X MK 2, and NAVIGAT 2100 / NAVIGAT 3000.
The repeater data (TTL) and single-ended signal lines share a common
ground connection, while data lines for general use (RS-422) are electri-
cally isolated from each other and are all-pole switched.