This document provides guidelines for the assignment of Vertical Service Codes (VSC) for which standardization or consistency is desired across all industry sectors in the Public Switched Telephone Network (PSTN). For the purposes of these guidelines, VSCs are customer-dialed codes in the *XX dialing format for touch tone and NXX dialing format for rotary phones. They are used to provide customer access to features and services provided by network service providers such as local exchange carriers, interexchange carriers, Commercial Mobile Radio Service (CMRS) etc. VSCs are assigned to features or services to enable consistent accessibility throughout the PSTN.

The purpose of common/standard VSCs is to minimize customer confusion and provide a standard service access approach for features and services within multiple individual networks (multi-network applications).