Connecting to Inter-tel system

For months I have been trying to connect my old inter-tel system to our asterisk box. And still have not found a way to connect these. I am looking for the easiest and cheapest solution to connect these two. has anyone ever been able to make this work? Please let me know. Thanks

not familiar with the inter-tel system.

Does it have some analog ports? If it does, I would connect to those with Asterisk - we did that with our old phone system until we upgraded.

You will probably need to discuss with your intertel phone maintenance folks how to work those analog lines in.