DATASONICS SIS-1500, System Manual

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4-8 DATASONICS
Volume I System Manual June 1998
9600 baud with the high voltage power along the coaxial cable to the subsea
electronics. The sonar key, which is first modulated by a 12.0625 kHz carrier
frequency, is also transmitted to the subsea electronics. And if a responder is
installed, a responder key, which is modulated by a 48.250 kHz carrier
frequency, is transmitted to the subsea electronics. The responder key is
either input to the multiplexer from an external source such as a navigation
or positioning system or generated by the Microcontroller board. The Cable
Interface also combines the uplink sonar data, the tow vehicle status
information, and the sensor data that are transmitted along the coaxial cable
from the subsea electronics. The uplink sonar data are transmitted at
1.544 Mbits/sec at frequencies of 90 kHz and higher using industry-standard
T1 telecommunications technology. This technology allows the sonar data to
be embedded with the synchronization and timing information for reliable
recovery by the T1 Receiver, which outputs the sonar data and clock signals
to the workstation as DATA OUT and CLOCK OUT, respectively. The uplink
vehicle status information and sensor data are transmitted at 9600 baud
using an FSK format, where the data are centered at 65 kHz. The data are
converted into RS-232 format by the Modem and output to the Microcontroller
board, which outputs the data to the TELEM serial port of the workstation.
Subsea Electronics
A block diagram of the subsea electronics is shown in Figure 4-3. Also refer
to the wiring diagram for the sonar electronics, which is shown Drawing
D150-08391.
The main components of the subsea electronics include the sonar
electronics, the port and starboard transducer arrays, and the standard and
optional sensors. The sonar electronics generates the Chirp waveforms,
transmits and receives the sonar signals, interfaces with the standard and
optional sensors, and communicates with the topside processor. The
transducer arrays transmit and receive the acoustic signals. The standard
sensors are the pitch, roll and heading sensors, and the optional sensors
include a temperature sensor, a pressure sensor, a cesium magnetometer,
and a responder, which is used to acquire tow vehicle positioning information.
All the circuit boards in the subsea electronics are contained in the sonar
electronics. There are eleven circuit boards in all, and their assembly drawing
numbers are listed below.