Question: During call setup, if a 'dual system' UE (supporting both GSM and UMTS) does not send a Supported Codecs List (DTAP) to the MSC, which codec type will the MSC assume is supported by the UE?
Option 1: FR_AMR
Option 2: UMTS_AMR_2
Option 3: UMTS_AMR
Option 4: GSM_EFR
Explanation: According to specifications for handling multi-mode configurations, if a 'dual system' UE (supporting both GSM and UMTS) does not provide a Supported Codecs List (DTAP), the MSC will assume UMTS_AMR_2 as the supported codec type. This is because UMTS_AMR_2 is designed to be compatible with both GSM and UMTS, allowing for seamless operation in TFO with GSM terminals, while also being fully compatible with R99 Core Network nodes.