short. It occurs in less than 300 ms and can be as little as 150ms when operating in DMO. This is much shorter than the time it takes for a standard cellular telecommunications system to connect. This is very important for the emergency services where time delays can be very critical. 10 Cellular telecommunications Today cellular telecommunications is an accepted part of everyday life. Its growth has been phenomenal and is seen as one of the technological success stories of the end of the twentieth century. This can be seen by the fact that in many countries some people have two or more phones. This growth has been seen across all areas of the population. Youngsters use their phones as much if not more than those people in other age brackets, indicating that in years to come use will remain very high as these people grow older. It is a well-known fact that the growth of cellular telecommunications has far outstripped analysts' expectations. Out of this many new companies have been created, and grown to rival some of the largest companies in the world in terms of size in just a very few years. Evolution The concept of cellular telecommunications dates back to 1947 at Bell Laboratories when an internal document proposed the idea of a system using a number of low power transmitters in 'cells' to enable frequency reuse in a mobile radio or telecommunications system. The proposal even mentioned the need for a method of handing over' the mobile station from one cell to the next as it moved along. However, the document does not state how this might be achieved. The system remained dormant for many years, and although a number of mobile phones were in use, these were relatively simple, effectively being a normal two-way radio system using one frequency for transmit and another for receive. On early models the user even had to use a press to talk switch. On top of this they only operated in populated areas, requiring a single transmitter to provide the required coverage. Naturally this was limited, as was the number of av