4-18
8011M ACOUSTIC DECK UNIT
0004811_REV_F
Status is usually reported by a string of pulses at either a 1 per second or 1 per 2 seconds and either 7 to
8 pulses or 14 to 15 pulses long. Pressing <ENT> will exit the listening mode.
EdgeTech Acoustic Equipment uses a 16-bit FKS code. The actual code that the operator enters is a six-
digit code. The first digit encodes the two frequencies used for transmission and must be between 1 and
6 inclusive. The last five digits represent the specific binary code transmitted, less a final parity bit, and
must be between 0 and 7 inclusive. Each underwater unit is supplied with a configuration sheet that shows
the commands and the frequencies used during ranging for that particular system.
4.3.3
Ranging <RNG>
The ranging function is used to determine the distance from the 8012M transceiver to the underwater
unit. Ranging can be done in Horizontal or Slant mode.
In
Horizontal Mode,
the deck unit calculates the distance between the deck unit transducer and the
underwater unit transducer after removing the underwater unit's depth from the equation.
In
Slant Mode
, the underwater unit's straight-line distance from the deck unit’s transducer is
calculated. To use horizontal mode, the user must know and enter the depth of each transducer.
The deck unit subtracts the deck unit's internal delays and the TAT (Turnaround Time) from the total two-
way travel time of interrogate and reply pulses to calculate the range. TAT is the total internal delay of
the underwater unit from the time a valid interrogate pulse arrives at the transducer to the time the reply
pulse is transmitted.
Ranges are reported in meters and milliseconds on the display when received. Time is converted to meters
using the speed of sound, which can be entered or changed using the menus. The default speed of sound
is 1500 meters per second. When using the repetitive ranging capability, enter a repeat time long enough
to allow the reply to come back before the unit sends another interrogate pulse. If trouble ranging occurs,
try lowering the transducer deeper into the water.
In most cases, when ranging problems exist, it is because the deck unit does not receive a reply. This can
be caused by the ship and surface noise, so lowering the transducer will help to avoid this noise. This can
also be caused by thermoclines reflecting the sound. Lowering the transducer can help by getting the
transducer below the thermocline or at least changing the angle to the thermocline. The user can change
the sensitivity setting, if it is too sensitive, the deck unit will report random ranges, and if it is not sensitive
enough, the system will report “no return.”
4.3.4
Serial Port Operations
The model 8011M acoustic deck unit has an RS232 port available. The port can be used to log activity or
to control the deck unit remotely. The 8011M serial port is always in logging mode when not in remote
control (host mode).
When logging the 8011M reports, range information, and any BACS command that has been sent. Each
logged line is followed by a carriage return and line feed. Logged ranges are reported as the total time of
