Provide the subscriber identity credentials that cellular equipment needs to authenticate with a mobile network. Yealink SAEUSFTC77SIM is a physical SIM card intended for equipment that accepts a SIM card, separating the subscriber credential from the cellular hardware itself. It is not a handset, cellular gateway, or connectivity plan; it is the card used to present a subscriber identity to a carrier network. A SIM card is installed in the equipment SIM slot and is associated with the carrier account and service arrangement selected for that device. This makes the card relevant where a cellular-connected endpoint needs its own subscriber credentials, such as equipment operating away from a fixed Ethernet or Wi-Fi connection. The receiving device must have a compatible physical SIM interface and support the required cellular service arrangement. This item is described as a Systems Application Enterprises SIM card and classified as a customer-owned product. Its role is limited to cellular subscriber identity: it does not add cellular radio hardware, provide a device enclosure, or replace a service subscription. Select it when the deployment requires this specific card code and the associated cellular equipment, carrier activation, and service terms have already been determined.