asterisk users - Sep 2016 - PRI error: link goes down when make calls

Hi.
These becomes from layer 1 issue and could becomes from a wide of  possibilities
(telco or Asterisk PRI card).
At first check cables an connectors, on Asterisk could make a loopback and check
if problem persist.
On telco should check cable of DSL Modem or whatever provide PRI service.

Mc GRATH Ricardo