Yes, it is possible to search for a free line across multiple line pools.
However, the system doesn't search the line pools in order. That is, the system doesn't search Pool A before Pool B, nor Pool B before Pool C. Instead, the system searches from the greatest line number to the lowest line number. That is, the system starts with Line 004, then Line 003 and so on.
So, if you want to pick lines in a particular order, you have to change the order of the lines on the distribution block. In your case, the fax line would become Line 001 and the other lines would become Line 002 through Line 004. I will use this line numbering in the rest of the post.
In other words, line pools cannot be used to choose the order in which free lines are picked. Line pools are used to restrict line access from certain sets. They are also used to route calls on specific lines, as luv2ski mentioned.
Here is what you need to program to search a free line across multiple line pools:
[ol 1]
[li]Put the lines in line pools. The lines can be in the same line pool or they can be in different line pools.[/li]
[li]Allow each set that needs to make outgoing calls to access the lines pools.[/li]
[li]Remove any line pool access code.[/li]
[li]Set the external access code to 9.[/li]
[/ol]
Now, when users want to make an outgoing call, they press an Intercom button (or pick up the receiver, if Intercom is their prime line) and dial 9. The system searches from the greatest line number to the lowest line number and selects the first free line. The system skips the lines that are in a pool that the set is not allowed to access.