The QX50 IP PBX is designed for your small office and supports up to 50 extensions. This solution offers two FXO analog PSTN connections, two FXS analog station ports and 16 extensions out of the box. The QX50 allows you to make up to 16 simultaneous IP calls. Like all other QX devices, the QX50 includes a Firewall, DHCP server, NAT, router and VPN engine suitable to connect directly to your broadband service in a small office. It supports over 16 external simultaneous calls. With Call Parking and BLF support on most SIP endpoints, the QX line can emulate key systems very close allowing for easy transition from old legacy systems. The QX50 has a redundant power connector that allows sharing power with another unit for redundancy. Most models come with an AUDIO In port for analog music on hold and an AUDIO OUT port for connecting to an external paging system. The SD card slot expands the available memory for call recording or voice mail storage.