Here in NJ, I don't believe that they are used either anymore. I do know that there are signals of different frquencies sent out over the track itself from the station to the train engine. There could be many different signals all running at the same time. The signals can tell where the train is, if the train passed a red signal, and it could even stop a train dead in its tracks if the engineer goes through a red signal. My nephew is an electrican on the RR now here in NJ.
