I am confused about one point I have read the following paragraph from the networking book.
“the twists in the twisted pair cable are used to avoid the unwanted signals. For example one twist, one wire is closer to the noise source and the other is farther; in the next twist the reverse is true. Twisting makes its probable that both wires are equally affected by the unwanted signal. This means that the receiver which calculate the difference between the two receives no unwanted signal.”

Now ok I understood the purpose of twists but I am confused about how receiver will calculate the difference when it will receive the signal?. How unwanted signal will be eliminated ? 
Another thing that I want to make clear is ,  I am beginner please provide such an answer that can be understood.


Question: Get latitude/longitude of friend's current_location using Graph FQL
Answer: fql?q=SELECT location,name FROM page WHERE page_id in (SELECT current_location.id from user where uid in(select uid2 from friend where uid1=me()))


this will do the magic for you