Jay Prime Positive <jpp@markv.com> writes:

A fourth is to use an externaly generated sync signal -- for example a radio transmission that both sender and reciever can hear. (For this aplication, I don't see how this would be used...)

Some spread spectrum systems synchronize using the (very accurate) time signals provide by Global Positioning System (GPS) satellites.

Aditional solutions are possible. (What is this S.A.W. thing I read about??)

I don't know where you read it, but it might stand for "Surface Acoustic Wave".