The reason for this is illustrated in Figure 1. The statistics help to determine reasons for failure. One of the commonest reasons for losses is weak fraud prevention. This is another reason for using copper. For this reason circuitry must be very linear. There are many reasons why plastic gears may be superior to metal ones. This is the reason why 16-PSK is not included. https://339efcb25eb75e967b0d-ff8eeadd950d51fd1fc939dca75b3973.ssl.cf1.rackcdn.com/assets_green.swf