TELECOM Digest OnLine - Sorted: Re: GSM-900

Re: GSM-900

Chris Farrar (
Sat, 02 Apr 2005 01:25:57 -0500

Jason <> wrote about Re: GSM-900 on Date: 1 Apr
2005 09:02:14 -0800

>> But since we transmit in x freq, then the receiver must tune to x feq
>> in order to receive the signal right? Why transmit at x freq and
>> receive at y freq?

> The answer is "Full Duplex" vs "Half Duplex."

Think of a Family Radio Service (FRS) walkie talkie. You transmit and
listen on the same frequency. If you're transmitting, you can't hear.
If you're listening, you can't transmit. Only one side can speak at a
time. If both transmit at the same time, you can't hear each other,
and anyone else on the same frequency hears garbage as you get walked

Transmit at X, and the other side transmits at Y, you listen on Y and
they listen on X. Thus both of you can talk simutaneously, like a
land line telephone.


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