Either op amps or comparators.

Contradicting the industry norm?
The are not intended to be an exact representation IMO, The fact the date sheet states that the input is Resistive which would equate to an Opto, and results in ~7 ma at 24v input.
Max.

 

In the schematic the triangles are comparators.

 

In the schematic the triangles are comparators.

And yet Again where is your confirmation of this ?
Max.

 

Look like comparators.