Section: 9.3.23.1.2 Bearer capability 1 and bearer capability 2
Content: The bearer capability 1 information element may be omitted in the case where the mobile subscriber is allocated only one directory number for all services (ref.: 3GPP TS 29.007[ General requirements on interworking between the Public Land Mobile Network (PLMN) and the Integrated Services Digital Network (ISDN) or Public Switched Telephone Network (PSTN) ]  [38]). The bearer capability 2 IE is missing at least if the bearer capability 1 IE is missing. If the MSC wishes to indicate capability for an altenative call mode, which can be entered through fallback, this is indicated by adding a bearer capability information element (bearer capability) 2 element (see subclause 5.3.6).