In the case of mdlPbxFraSignalMode = userDefined(5), this field defines the A,B,C Bits. D bit is supplied for future versions. Bit 1 = Bit A ON Hook - Local Bit 2 = Bit B ON Hook - Local Bit 3 = Bit C ON Hook - Local Bit 4 = Bit D ON Hook - Local Bit 5 = Bit A OFF Hook - Local Bit 6 = Bit B OFF Hook - Local Bit 7 = Bit C OFF Hook - Local Bit 8 = Bit D OFF Hook - Local Bit 9 = Bit A ON Hook - Remote Bit 10 = Bit B ON Hook - Remote Bit 11 = Bit C ON Hook - Remote Bit 12 = Bit D ON Hook - Remote Bit 13 = Bit A OFF Hook - Remote Bit 14 = Bit B OFF Hook - Remote Bit 15 = Bit C OFF Hook - Remote Bit 16 = Bit D OFF Hook - Remote In conjunction with the Mask, mdlPbxFraSignalMask, it is possible to compute the signal mode.