When two technicians are testing outside plant, one will ask the other to short the pair at his end. Then with an ohm meter, you can read the total loop resistance, and knowing the expected distance, and the ohms per foot for the type of cable, calculate what you _should_ see on the ohm meter. If it is wildly out of range, there may be a "dirty" splice along the way, adding series resistance to the loop which will result in imbalance and static. In this situation, it is time to break out the TDR to find out where in the loop the problem lies.
When testing in house cable, connect your toner to one end of a pair, and when you find the tone at the other end, put a short on it. If the tone stops when it is shorted, the pair has continuity all the way through. If the tone continues, one side of the pair is open.
A couple of days ago, I had an electrician run a Black, Filled, underground cable from the 2nd floor suite to the Telephone Equipment Room. When he punched down the end in the suite, he lost the twist of the pairs. On filled underground cable, there is no tracer on the wires. There are 5 white wires, and there are 5 blue wires. If you lose the twist, you don't know which Tip goes with which Ring. I punched down the Telephone Room end, (properly, of course), and put a short on EACH pair. Then using the continuity function of my toner, I was able to sort out which Tips and Rings made up the pairs, and repunch his work.