Does anyone have knowledge of how phone calls could be traced in the 1970s (if this could be done at all)?

On old TV shows like Five-O, there is sometimes "call tracing" seen as a plot device, which usually fails because there is not enough time to complete the procedure.

I found this posting on some WWW site:

In the days of mechanical exchanges, all traces of a local call would vanish within a fraction of a second after hangup, as steppers would get reset to home position in preparation for another call. I don't know if any such exchanges are still in use in the USA; the last time I used one was in 1994. While such exchanges are rare if not non-existent, they established the convention that phone traces are performed at the Speed of Plot, and the convention has persisted even when the reason behind it didn't.

On Five-O, in order to >really< trace a call, you would have to have someone waiting at the phone company to do this. You can't just pick up a phone and call someone at the phone company and they can produce immediate results. (This almost always fails.) You would have to plan the trace ahead of time. Someone at the phone company would be in a back room at the phone company where there were all these racks of wires and switches, and could somehow track down each number of the call (or so it seems) ... if they had enough time.

In some H50 episodes, they are able to determine if a pay phone was used to make a call, but I think that applies when the call was international, because then there would be a record of that for long distance billing purposes.