How to differentiate between a full signal icon and an empty signal icon on my Andriod Device? My question is not a duplicate of this post as in that the OP is asking for the difference between the network icons for a rooted device  whereas mine is for mobile signal icons in an un-rooted device.

Mine is a Samsung trend  phone with Android 4.1.2.Every time i check my phone for any signals it shows full but in the notification tab(the area displaying the network name) displays no network.

When there is 1 bar and not greyed out i am able to receive messages but when it's full with a surrounding grey box there is again no network and some times it also display's a small triangle with an exclamatory symbol in it when the phone signal is completely empty bars.

I am confused and unable to differentiate how does Android 4.1.2 display the different availability of phone signal icons.(i.e. No signal,Full signal, etc)

Note:-I would be adding the screen shots of the device shortly .
The "no network" in the notification tray doesn't mean there's no signal: it means your phone isn't allowed to use the network it's connected to. For instance, this might happen if there's no SIM card. In this case, your phone's not allowed to make normal phone calls, because it can't identify you as a customer, but it still connects to the network and can make emergency calls.

It might also happen in an area where your operator has no coverage, but there is another phone network there. Again, you can't use it because you're not their customer, but your phone can connect to the network and make emergency calls.