This week I have (whilst not working) been watching Torchwood and the second disc of Ultraviolet (television drama, not the movie) which I have rented.
Both deal with secret government organisations and I like them both, but this scenario (which could be common to both) demonstrates how they are slightly different.
Bad guy uses a payphone whilst being watched by a good guy whom the bad guy doesn't know is following him.
Torchwood: phone someone operating a computer who access the phone network and track the call, discovering the destination the number and location. They'd likely pull up a handy nearby CCTV camera to get an image of their face too.
Ultraviolet: good guy picks up the phone after the bad guy is done and presses redial.
Back to work...