I've used OPTO for several years although not in my current situation. I have nothing but good things to say about their product line.
Although, I do have one *****... they don't have Manual Switches on their Output Modules at all (a very convenient FORCE at the panel) and they don't have Manual Switches on any of their Input Modules rated for anything over 5VDC Control Voltage.
Other than that, I was very pleased at their dependability, durabilty and module color coding. Typical price for an Input or Output Module is $5.00 (SSR or Relay). A half-dozen modules fit easily into your pocket.
The last time I checked they still don't have Opto-Isolator Modules. I really wish they did. It would make my life less painful.
A Pheonix Opto-Isolator goes for $50.00! OUTRAGEOUS! I can buy an Isolator chip for less than $0.50 and a power transistor for less than $1.00. Of course there is assembly, package, blah, blah, blah.
They (OPTO) also have a Controller called "MYSTIC" that they've been selling for about 10-years. This too is very good.
I used the PC version of OPTO and was very, very pleased with it!
And, as I recall, they could handle the NPN vs PNP Input problem by arranging the modules in a certain way. I made a post to... damn, can't remember who... but it addressed the NPN vs PNP Input problem specifically.
Was it you, George?