Let's start with the fact that the role of the OGRE can be an optocoupler, relay (I know about solid state only) and the transformer.
The challenge for discrete inputs and outputs to find the OGRE on the following parameters: for input voltage equal to 24V, the current is unimportant; for output voltages 110 VDC and 7 A. confusing information in dataset and directory chipdip.ru because you have specified the control parameters and input parameters. Apparently you need to look at the input parameters, but to find those criteria that you set, almost unreal, where did not specified features. Specify where to search or maybe some other way out of this situation? Well, maybe I don't understand it?
And as an example 6N137: www.platan.ru/cgi-bin/qwery.pl/id=7043&group=21001
The parameters are as follows: "direct input voltage" "maximum input voltage" and "maximum voltage". Well how can that be?