NEC SL2100 & SV9100 overview - The product is a hybrid offering with on-premises hardware and secure cloud-based hosted options. You can have dedicated hardware that starts with the main control unit with four slots on the 2100 to which you can add up to 3 expansion modules to around 100 extensions. The 9100 goes up to over 800.
Line options - You have a choice of SIP/VOIP, analogue lines (single or in groups), ISDN2E pairs of digital lines with option for DDI numbers (direct dial in), ISDN30E digital lines for 8 or more lines again with DDI and VOIP lines also known as SIP trunks which connect to the system via broadband, leased line or other data circuit.
Handsets and users - NEC offers a wide range ranges of both digital and IP handsets as well as branded analogue handsets (you can also use any PABX compatible analogue or DECT cordless), mobile twinning as well a PC and mobile softphone (Android and iOS).
DECT - There is also an advanced integrated DECT system which is useful for warehouse or campus style installations where users need rugged DECT handsets with a base station setup that covers the entire relevant area and crucially can handle several calls on each station and hand calls over between stations as people move about.
Mobile user standard integration - at it's most basic level you can forward calls from your extension to your mobile (using ISDN or SIP lines). Your mobile users can transfer callers and make calls through the phone system which will then be recorded and logged if applicable (see below).
Mobile user advanced integration - at the advanced level your smartphone can integrate and even make/receive the call via 4G or wifi where available (they can still use the mobile network). This allows office and mobile staff to communicate with mobile staff using company instant messaging rather than having to switch to personal skype or Whatsapp. If enabled office users can also see the geo-location of mobile staff on a map (using the phone's on board GPS) - great if they need to update a client with an ETA without having to call someone who is driving. Mobile users can also handle their voicemail messages via on screen interface buttons. Again calls made through the phone system will then be recorded and logged if applicable (see below).