Many PABX systems installed in offices have a part that is capable of doing DECT. Many system vendors now also offer hybrid systems, where communication with voice over IP, or with the classical phone network are possible. In such systems, the communication with the handsets is done using DECT, and the PABX is capable of doing SIP. Some vendors propose WLAN-based solutions to connect the handsets, but this solution is often more complex than using DECT.