Which three devices can be used to interface with the public switched telephone network? (Choose three.)

Cisco Unified SRST provides local IP PBX fallback call processing for branch sites during WAN outages but does not itself provide a physical or logical interface to the PSTN.

Cisco Unified Border Element (CUBE) functions as a SIP demarcation point between the enterprise voice network and PSTN service providers, providing direct IP-based trunk connectivity to the public telephone network. It terminates SIP sessions from the carrier side, making it a true PSTN interface device.

Foreign Exchange Office (FXO) ports connect to the PSTN by interfacing with the telephone company's analog loop, simulating a phone set connected to the central office. FXO is explicitly designed to terminate PSTN analog lines into the enterprise voice infrastructure.

The Cisco VG224 Analog Voice Gateway primarily provides FXS ports for connecting analog end devices such as phones and fax machines to the enterprise network, not PSTN trunk interfaces.

The Cisco E1/T1 ISDN PRI Network Module provides digital PSTN connectivity via Primary Rate Interface circuits, which are carrier-grade TDM connections delivered directly from the public telephone network to the enterprise.

Foreign Exchange Station (FXS) ports supply dial tone, ringing voltage, and power to analog endpoint devices like telephones and fax machines, connecting internal devices rather than PSTN trunks.