Error 0x80EE007F

Value: -2131885953 | 0x80EE007F | 2163081343

What does it mean ?

RTC_E_SIP_REFER_OPERATION_PENDING  
Currently a refer operation is pending
Value: 127 | 0x007F | 0b0000000001111111

Where does it come from ?

FACILITY_RTC_INTERFACE  
RTC - Real-time Communications
Value: 238 | 0x0EE | 0b11101110

Other Errors for FACILITY_RTC_INTERFACE