This document gives an overview of telephone voice interconnect for Land Mobile Radio (LMR) systems. The representative functional network model given in Figure 1 of this document describes a telephone interconnect interface Et, and it is the purpose of this document to describe how telephone service is accessed through the Et interface by an LMR system.

Note that, in the System Model Reference Configuration shown in Figure 1, only the interfaces are shown. Thus when referring between this overview and Figure 1, no attempt is made to allocate specific functionalities to particular elements within the RFSS. Further, this document does not describe the ergonomic interface to radio equipment for telephone interconnect service. Note that features and services for which support is described by this document are not necessarily supported by the telephone network connected at the Et interface. Describing these features and services does not predicate their presence in the telephone network being accessed.