Computer program can keep follow us, we need a device that could detect our position. The device that could detect us is use threeliteration technique that use ultrasonic wave, the wave that had frequency above human sound frequency. The technique that in use is similar with GPS (Global Positioning System) technology. In threeliteration, we can determine object location precisely with three reference point.
If reference point A is located at Distance a metre from object that we will locating (X) then we can know that X could lay down everywhere along circle circumference with radius a metre. Ultrasonic wave streak along this line. The distance (s = v x t) between point A and X are able to know from time (t) that ultrasonic wave needed to reach point A since release by a device (object X). The streak velocity sound wave (v) on air is constant that had knowing. The distance between reference point B (b metre) and X could be determined with the same way. From this two information about the distance we can find two possibilities about X position , that between both cutting point two circle. Then with the same way again the distance (c metre) between referencepoint C and X could be determined. With this last data we are able to discover X position precisely on two dimensional plane.
The device that used to radiate Signal is called 'bat'. Bat can be brought everywhere (because of its small size and had form similar to pager) and we can pose it on our clothes (like posting cellphone to pants belt). Each bat have unique code that function as its identity (ID) so that won't be an error even our friends in another room are also use bat that radiate signal. It means, wherever we go, we still could be detected (with accuracy till 3cm from actual location). Our location is always detected if in our surroundings there is signal receiver that receive signal from the bat we brought. This receivers are posted along roof inside surface in all buildings, rooms, or our home. The distance between this receivers is about 1.2 metre (about 4 feet). To find the location of bat (green ball), only three receivers (act as three reference point in threeliteration technique) closest that need to work. In one room that has area 1000 m2 will installed 720 this small signal receivers. The perfect example of room that had uses this system is AT&T Laboratories in Cambridge.
Besides ultrasonic wave, a bat had also function to radiate and receive radio wave as telecommunication medium with Center Computer (prime tool control) that control overall system. When we want to find bat's location, the center computer send radio signal that containing ID code the bat that we look. Bat receive this radio signal and straight immediately send ultrasonic wave that containing similar code in form binary digit to three closest receivers.
The center computer are also has the data about all computer location and other electronics device inside building. After bat's location determined with threeliteration, the center computer immediately find the location of computer or electronic device with the closest distance to the bat's location. Automatically that computer become similar with our computer, with all data and programs that only store on our PC. Beside the computer, this system had also able to used on other electronics and communication device such as Telephone. Automatically, the closest telephone to us become our telephone. It means, when there is incoming call, the closest telephone can be used to answer it. All do in automatically (of course with the help from computer!) without call forwrding process from one telephone to another. If the closest telephone to us is suddenly ringing, we can answer it immediately like we are being in our home because that telephone has become our telephone. So that, this technology can be called the system that always follow us wherever we go, like we only need to give command 'Follow Me...!' to all that our electronics devices.
This ultrasonic location system technology are true mobile because it can keep moving everywhere. The term mobile computing is not limited anymore to notebook ar PDA (Personal Digital Assistant) that can be brought everywhere but still need data transfer and program that wasting time. We still need notebook and PDA and other mobile device if we go outside building or home that has this Follow Me....! technology. But when we walk around inside building or home we still can enjoy 'faithfulness' of the system like shadow. With this system, our computer and our electronics device can be 'teleported' to wherever we go. This network that like being everywhere like this that the next day will surroundings us in the future. Rapid progress any research that does today enhanced possibilities the readiness of thistechnology in the next few years.
