With several hydroacoustic systems in use simultaneously, interference may be a problem. The Simrad TU40 Trigger System fixes this problem by synchronizing sonars, echo sounders and other hydroacoustic systems.
The Simrad TU40 is developed for fishing vessels as a small and intuitive system for synchronization purposes.
On research vessels, the hydroacoustic system are the main scientific tools. Nothing can disturb the received echoes, as this will make the echo data unusable for the scientists. For this reason, the K-Sync was developed. It controls the transmission for all the hydroacoustic systems onboard the vessel, synchronizing them in groups by the transmission rate.
However, the K-Sync is too powerful for fishing vessels. That is why we developed a similar concept for fishing, the Simrad TU40 Trigger System. This system is dedicated for fishing vessels. You specify a chosen system as "master", and the TU40 distributes the transmission control to all other hydroacoustic systems on board.
What THE SIMRAD TU40 does
In this example from a Simrad ES80 echo sounder, compare area (A) with area (D) to see what the Simrad TU40 does.
(A) All the hydroacoustic systems on the vessel are synchronized. The echogram is clean and you can identify small fish.
(B) Two echo sounders are in operation, but they are not synchronized. You can see that the interference disrupts the echogram, as the number of short pulses increase.
(C) Four sonars have been started, but these are not synchronized. The interference is stronger, and it is very difficult to see any targets.
(D) All the hydroacoustic systems on the vessel have been turned on. The echogram is completely disrupted with interference, making the echo sounder useless.
The TU40 has twelve independent channels. All the channels are isolated, and the unit is compatible with most commercial hydroacoustic equipment, not only with Simrad equipment.
The Trigger Unit runs autonomously. It is set up from a commercial computer running the TU40 program. This application provides the user interface, which allows you to monitor status, settings, and transmit trigger schedules. Once setup is completed, the TU40 program can be closed. The computer can be disconnected from the Trigger Unit, and even put to other use.
Whenever more than one hydroacoustic system is installed on a vessel, interference may occur. To avoid interference, you can either set up one of the hydroacoustic systems as "master", or connect all the sonars and/orecho sounders to a common synchronization system. By means of trigger signals, a common synchronization system will provide individual control of each sonar and/or echo soundertransmission ("ping") sequence.
"In physics, interference is the phenomenon in which two waves superpose each other to form a resultant wave of greater orlower amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other,either because they come from the same source or because they have the same or nearly the same frequency. Interference effectscan be observed with all types of waves, for example, light, radio, acoustic, surface water waves or matter waves."
https://en.wikipedia.org/wiki/Interference_(wave_propagation), April 2016
The TU40 permits each hydroacoustic system to transmit ("ping") according to a logic trigger pattern established to avoid interference. This pattern is made by defining one or more hydroacoustic reference systems, and give these transmit priority. Systems operating in the same frequency range are permitted to transmit simultaneously.
The Trigger Unit consists of a programmable logic controller (PLC) and other electronic circuitry that provide the synchronized trigger signals. The standard Trigger Unit can control up to 12 hydroacoustic systems.