Hey I am using 2 4N35 Optocoupler from Visha can I replace them with a single ILD615 from Vishay?
This is one possible way of using opto-coupler:



This is PC817 and lacks a base connection. Most likely you also don't need it. This circuit will generate a HIGH Output when there is a HIGH Input.

In this case, you can use ILD615 if you need a dual channel. Connections will be similar. You don't to worry about base connection.



Compare the two images and you will know how to connect everything.