Telephony subscribers in internal areas can take part in voice communications and, in the LANCOM VoIP environment, are referred to as "users". The LANCOM differentiates between:
- ISDN users
- A maximum of 40 terminal devices connected over the ISDN network, including ISDN and analog devices connected to an upstream ISDN PBX. When connecting downstream PBXs to point-to-point lines, the number of possible ISDN subscribers is determined by the length of the extension number (DDI). In this case, all of the telephones and terminal equipment connected to the PBX can be mapped with a single ISDN user entry.
- SIP users
- A maximum of 40 (with the LANCOM VoIP +10 option) SIP terminal devices connected over LAN and WLAN and analog devices connected with an ATA.
The external paths of communication available to the users are known as "lines". The LANCOM knows the following lines:
- ISDN
- A connection to an ISDN NTBA over the TE interface. The NT interface can additionally be used to connect ISDN terminal devices directly or via a downstream ISDN PBX.
- SIP lines
- A maximum of 55 lines (with VoIP +10 option) are possible. There are three different types of SIP line:
- A "Single account" line acts like a normal SIP account with a single telephone number. The internal users can all make use this account for making SIP calls, although only one call can be conducted at a time.
- A "trunk" line acts like an extended SIP account with a main external telephone number and multiple extension numbers. Internal users use this account in parallel and several calls can be made simultaneously (until the maximum available bandwidth is exhausted).
- As a "SIP gateway" line, the LANCOM VoIP router provides a remote SIP PBX with a transition to the local ISDN network. The SIP gateway is registered at the SIP PBX with a single number, although several calls can be conducted at once (until the maximum available bandwidth is exhausted). The connection between the SIP PBX and the LANCOM VoIP router is normally established over a VPN connection.
- SIP PBX systems
- Maximum 4 connections to upstream SIP PBXs. These lines are generally connections to large PBXs in the network at headquarters which can be reached via a VPN connection.
Note: The precise number of users and lines available varies between models and software options.