What are the different signal indicators avalable on the notification bar? The signal indicator on my phone often shows "3G" or "H+" in the signal indicator. When there's no connectivity it doesn't show anything.

I'm referring to the icons in the status bar like these:

  

What are the different signal icons that are shown in android? I've never used an LTE/4G handset or even been on one of those networks so I'm also curious to see what indicators are used for those.
They are referring to the mobile data connection:


1x: 1xRTT (slow like a dialup modem (here: 80–100 kbit/s), shows up on US Cellular CDMA networks with Google Fi in Northern California)
G: GPRS (slow like dialup modem, here: 56–114 kbit/s)
E: Edge (enhanced GSM, about 400 kbit/s)
3G: UMTS (384 kbit/s to 7.2 Mbit/s)
H: HSPA (enhanced 3G, sometimes shown as 3.5G; up to 21 Mbit/s)
H+: HSPA+ (even more enhanced/faster HSPA; up to 42.2 Mbit/s)
4G: LTE (thanks to eldarerathis for confirmation); up to 300 Mbit/s
5G: not yet in the wild; up to 10 Gbit/s planned


The bars obviously show signal quality, and the arrows show whether data transfer is in progress. As for the colors (your pictures show blue and gray signal icons), please refer to What does it mean when the connectivity icons in the status bar go white/gray?