The selector (SEL) is a data field in the ATM address. It is a 1-byte subfield in the setup message of ATM.
The selector was specified by the International Standards Organization (ISO) under ISO 10589 and, together with the End System Identifier (ESI), forms the user-specific part of the ATM address. The selector is only used for ATM end systems, not for ATM routing. The selector handles multiplexing to local end devices.