How to forward an incoming call when a line is busy


We have a fairly simple setup, with 4 incoming pots lines connected to a TDM400 with 4 FXO modules. 2 of the lines are dedicated to the 2 specific users, so they can still have a direct phone number as opposed to having to use an extension. The problem is this: When they call out, or when someone calls them any additional calls to that phone number ring busy. Is there any way I can detect the incoming call and put it right to their voicemail even though the line is busy, or do I have to use some type of call busy forwarding through the phone company. This seems like it would be a fairly common problem but I can’t figure out a better way to fix it. Would moving to a T1 fix this, and if so how?

One other alternative is to get a DID (direct inward Dialing) block of numbers from our service provider and then forward the line when busy to one other phone number (that you don’t give out so shouldn’t ever be busy), but all these features cost money from our provider and we’d like to stay away from that if possible.

Any help would be greatly appreciated.


I dont think your going to fix it with out a little $ going to the phone company.
Not knowing who your provider is but here we got bellsouth.
I have some rolloverline. 1 number going to 4 different phone lines so when someone dials the number it just goes to the next avalible line.

DID I have these as well so you can have multiple numbers on each line.
Say toiy have the following numbers 000-1234,000-1235,000-1236.And you have 6 DID lines the numbers can come in on any of the 6 lines The phone COmpany passess the DNIS or 000-1234 to you the asterisk box sees this and routes the call accordingly

T1 or more common PRI work in the same way as the DID except you On a PRI you get 23 lines out of a single interface