The three most popular cellular service in the United States are normal analog cell headphone ( AMPS ) , digital electric cell headphone , and PCS.Analog cellular serviceis the subject ofHow Cell Phones Work , so you’re able to study all about it there .
There are two popular digital system in the United States . One is generically known as " digital overhaul , " and the other is clearly branded as " PCS . "
" Digital service"uses digital phones , but they communicate with normal AMPS tug . A call is position up using the normal AMPS protocol , and then the conversation is carry digitally . ( assure outHow CDs Workfor info on changing analog signals to digital signal . ) Digital speech sound chop up a single AMPS vocalization channel into three digital channels using a technique calledtime division multiple access(TDMA ) . All that means is that three earpiece can share the same channel , and they each understand that they will only apply the TV channel part of the time . So one phone uses the channel for a subset of a second , then the 2d phone uses it , then the third , and the cycle per second repetition . Digital cellphone phone , as you’re able to see , are a hybrid between the existing analogue system and digital technology .
PCSphones are completely digital . They use a whole separate stage set of towers and a whole separate set of absolute frequency – between 1.85 and 2.15 Gc ( gigacycle per second ) . Because of the higher absolute frequency , there must be more tower nigher together . Because it is completely digital , encryptionanderror - correctingcodes can make the call much clearer and nearly unimaginable to intercept . PCS normally wad in other services like paging , caller IDand evene - mail .
