What is the meaning of the different LEDs on the Physitemp Homeothermic controller (TCAT-2)

The Homeothermic Controller for mice and rats (physitemp TCAT-2) has a few LEDs on its front panel that are not described in the owner's guide:

OUT1 and OUT2 refer to the control outputs which signal the power circuit to supply power to the heater or load. OUT2 is not used but OUT1 will flicker on and off as power is supplied  to the heater or load. 
AT pertains to the controller being in autotune mode which is part of the programming steps and not normally accessible to the user. 
AL1 and AL2 are alarm outputs which are not available to the user on this controller.  
PRO is the Program Running lamp which is only illuminated on programmable units and not relevant to the TCAT.

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