Signal question

After a round-trip between 33rd Street and Hoboken this weekend with myself squarely in front of the railfan window, I've come away with one question regarding the numbering of signals. Most follow an increasing/decreasing sequence and have the letter 'Z' under the number (for example, 143/Z is just prior to the Christopher St. station when heading toward 33rd), but some don't sit the sequence and have the letter 'X' underneath (e.g., R4/X just before the switches ahead of 33rd Street, and L4A/X and L4B/X at the edge of track 1 in Hoboken).
I'm guessing that the 'X' signals are the dispatcher-controlled ones, and the 'Z' signals are automatics; would this be at all right?

Thanks.

Well, to just about answer my own question (for the benefit of anyone else who might be interested), after my ride into Hoboken last Friday (railfan window again), the 'X' signals seem to protect switches while the 'Z' signals seem to protect blocks.

That pretty much covers the basics. Signals in one direction are even numbers, and the ones in the other direction are odd numbers. The first digit tells you which set of tunnels you're in. If extra signals were added after the original design, you get alphabetic suffixes in the sequence, like 146, 146A, 146B, 148.

The L#A / L#B are at entries to diverging switches, and were originally the lever number on a switch machine. The matching R signals are facing the other way into the same switch.

In general, the L#A/L#B are "bottom left, top right". There are some oddballs like the one in tunnel A in NJ at the junction to select Hoboken or Pavonia. It has a L/R lightbox next to it to indicate direction. Of course, when the tracks fan out to a 3- (or more) track station, things get more complex. Again, there will be a "Track #" lightbox next to the signal.

Many Z signals are timers as well as indicating block occupancy - a double yellow indicates a timer, while a single yellow indicates an upcoming block is occupied. So you can see a signal go from red to single yellow to double yellow.