Keypad expansion

With a keypad expansion, additional function or dial keys can be added to a telephone. These allow convenient dialling or calling specific functions by simply pressing a few keys. Keypad expansions are available in many different models and by various manufacturers. They have to be compatible with the respective device or the telephone system in use to be able to link them to a telephone. They are connected to the telephone either with cables or by directly connecting to the extension interface existing in the telephone. The power supply for the expansion model can be provided by external mains adaptor or via the telephone, depending on the model. A standard feature of keypad expansion generally includes LED indicators for conveying status information. Some devices also have a separate display and can show comprehensive information on telephone calls or functionalities.
The configuration of the keypad expansion depends on the model and is possible using various methods. Keypad expansion of a VoIP telephone can usually be programmed conveniently over a web interface and a graphical user interface.