The NEC SL2100 is a premises-based PABX system for small to medium businesses that offers a cost-effective, scalable hybrid TDM/VoIP solution for 4-60+ users. It includes built-in Unified Communications (UC) features like auto attendant and voicemail, supports mobile and IP DECT phones, and can be expanded to 256 ports or 112 IP terminals across multiple locations. The SL2100's advantage is its integrated applications, reducing the need for separate hardware and subscriptions, which puts advanced communication features within reach of smaller businesses.