Comcast PRI and Credit Card POS

[Drue]

I have a customer who recently changed from POTS to a Comcast PRI. I wired an analog extension out to the credit card machine and it works 40 percent of the time. Is there anything I can do (other than go back to pots) The circuit is set to g711. Any ideas would be helpful. First time we have used a Comcast PRI.
Thanks

 

[belevedere]

What system is this?

 

[Drue]

SV9100

 

[belevedere]

SLT specs
Standard (-28V)
Long Line (-48V)
What is your CC machine spec'd out for with regard to power?