What is the "RT" meaning in this circuit?
They look like  Resettable PTC fuses I have used before. 

R - Resettable T - Thermistor?  I am not sure about the abbreviation/references.

If it is the above device, the resistance of the poly fuse (ptc) rises as current goes above the rated limit in order to proctect circuity. 

They reset back to normal resistance once overload has disappeared and the part cools down.