Patent ID: 6657971
Filing Date: 2003-12-02
Classification: H04M,H04Q,Y10S

Abstract:
A method for detecting a loopback condition on an ISDN primary rate interface (â€œPRIâ€ ) by a telecommunications switching system, the method comprising the steps of:storing a call reference value (â€œCRVâ€ ) of a call SETUP command most recently transmitted onto a primary rate interface as a last sent call reference value; determining that a command has been looped back on the primary rate interface when a call SETUP command is received requesting an occupied primary rate interface channel with a call reference value equal to the last sent call reference value; incrementing a loop counter each time a command is looped back; determining that a loopback condition exists on the primary rate interface when the value of the loop counter exceeds a predetermined threshold; and resetting the loop counter to zero when a valid response to a transmitted SETUP command is received on the primary rate interface.