Will Asterisk work without internet connection being down?

i’ve got asterisk@home 2.8 with 3 voice T1s connected to a firewall/router.
I also have a Data T1 for the internet connected to the same firewall/router. And i’ve got about 15 sip phones connected to a switch that’s connected to the same firewall/router. Whenever the Data T1 goes down, I cant receive any calls through the Voice T1s. Is there a way for me to keep the phone system up even if the internet connection is down?

In an earlier post you said you had 3 PRIs for voice. Which do you have, PRI or T1 lines?

Why are the PRI lines connected to a data router?

In response to your other post…

If your telco supports it, you can share a D channel between PRIs. The downside to this is that if the PRI line carrying the D channel goes down you are down across the board. The upside is that you can have an extra two B channels available.