FreePBX connected to a foreign PBX - How to dial extension on foreign PBX?

My home FreePBX system treats my office PBX (an Elastix system) as a trunk. The Elastix PBX sees my home FreePBX as an extension. Everything works fine. However, I can’t figure out how to dial other extensions on the Elastix PBX. If I dial the 4-digit Elastix extension number, FreePBX treats it as a FreePBX extension which, of course, doesn’t work.

Can anyone help?

You just need to route those ‘extensions’ through that trunk, which is what outbound routes are designed to do, the wiki will help you there.