Provisioned to work with Office phone service only. Cisco's small business Spa 504G IP phone features exceptional voice clarity and enhanced speaker quality. It has a 2-port fast Ethernet switch with PoE (power over Ethernet) support, a monochrome LCD display with backlight, 4 line keys, 4 soft keys, and a 2.5 mm jack connector for optional headset. It supports up to 8 simultaneous calls.