asterisk users - Jun 2015 - Help With Physical Layer (Tony Kasule)

Tim 

At first should take a look to cable pinout (RAD documents) as  pin 1,2,
Transmit (output) and 4, 5  Receive (input) for Digium card  you should use a
straight cable (try to test with new cable one too).
Second check Dahdi configuration parameters, use dahdi commands as; dahdi show
status, service dahdi restart and check  result, (could a mistake on parameter
value on system.conf).
 
Mc GRATH Ricardo