The mark unit has two functions. First, it calibrates for the speed of sound in the water, which is a function of both the salinity and the temperature. See the section on calibrating for the speed of sound for details. After the speed of sound has been calibrated, the mark unit automatically switches to its second function - transmit mode - where it just simply sends out the simultaneous radio and acoustic signals. While this all may sound very easy, much innovation has gone into making it so simple.
The mark unit shown in the accompanying picture is 71" (1.8m) long. It operates on 4 AA batteries. In transmit mode it sends out the radio and acoustic signals about 5 times a second. The radio transmitter is low power and operates in the ISM band so no licensing is needed.
Just attach the unit to a mark, turn it on and set the mark. The unit calibrates the speed of sound through the water and then automatically switches to transmit mode. It really is that simple.
The boat unit receives both the radio and acoustic signals from the mark. The radio signal contains the calibrated speed of sound. The boat device uses this calibrated data to convert the time delay between the radio and acoustic signals into a distance. The boat unit is pre-programmed so it knows the appropriate size of the zone for the boat on which it is being used, and how to measure that from the point on the boat at which the acoustic receiver has been placed. See the section on measuring from the back of the boat for more details.
The main body of the unit shown in the accompanying picture is 11" (28cm) long. It operates on 2 AA batteries. A thin coax cable runs from the main body to the acoustic receiver. The tube forming the main body is transparent. This is so a logo or name of the group sponsoring use of ROAB for the regatta can easily be inserted into the tube and seen by all.
All ROAB signals to sailors and judges are issued by the unit on the boat. ROAB divides the area on the water into four regions:
1) The general sailing region - This is the region between marks where the zone is not an issue. ROAB is outside the range of the radio and acoustic signals from a mark. In this region the boat unit flashes green once every ten seconds so all can know the unit is on. If the boat unit has a low battery the green flash will be immediately followed by a red flash.
- general sailing region signal: green flash once every ten seconds
2) The activation region - This is the range from the mark within which both the radio and acoustic signals are received by the boat device. Within this region the boat unit flashes green once a second. In this region if the mark unit has a low battery the green flash will be immediately followed by a red flash.
- activation region signal: green flash once a second
3) The warning region - This is the region one boat length beyond the zone. Within this region the boat device will issue a red flash once a second. The boat unit will also make an audible beep once a second that accompanies each red flash. While the visual queues are for the trailing boat, the audio queues are the for the crew on the lead boat. There is no battery indicator mode in this region.
- warning region signal: red flash once a second
4) The Zone! - Within this region the boat unit flashes red five times a second. For the first five seconds within the zone there will also be an audible beep accompanying each flash. The audio only runs for five seconds (25 beeps) because there is no need to have an audible signal the entire time the boat is within the zone. There is no battery indicator mode in this region.
- in the zone signal: red flash five times a second
The general idea is that the flashes begin green and slow. They transition to faster rates as the boat nears the mark. At the point when sailors and judges need to be aware of the zone's proximity the flashes transition from green to red and an audible signal is included.
As one very small example of how the ROAB system innovates by using parts in valid but unintended ways, consider the information display (not shown) used during testing and development of the boat unit. It is a four character LCD display using standard seven element characters. When the device is first turned on the message "hello" is displayed. How can a four character display show a five character message? The message is not scrolled across the display, it is shown as a static presentation. To see the answer, click here. Yes, it is obvious once the solution is made clear. In that vein there are many such little innovative ideas that went into the design and development of ROAB.
The patent covers the innovations on how to assemble the sub-systems which add together and perform the ROAB functions. But it is the innovations held confidential as trade secrets which make the sub-systems simple, efficient and capable.