In debugging process, only one ISDN terminal can be called by MCU, but all three ISDM terminals can be called by digital phone.
“No load capacity ” or “No available information format element”
Upgrade MCU to version 2.13, and upgrade terminal to version 2.71.
The ISUP signaling is not opened between MCU and terminal, so the function of end-to-end digital call is unavailable. However, after MCU and terminal escalation, the function of speech call is available. So, even ISDN line does not use ISUP signaling, the ISDN terminal can be joined into conference successful.