The KX-TES824 is a modular system. Base unit supports up to 3 CO lines and 8 extensions, but with expansion cards (KX-TES824EXUS, etc.), it can grow to 8 CO lines and 24 extensions. Unlike VoIP systems with web GUI, the TES824 relies on a hybrid approach: feature codes or proprietary software (Panasonic KX-TE Maintenance Console).
There are two primary ways to configure the KX-TES824, as outlined in the Panasonic Programming Manual : panasonic kx-tes824 programming manual