The double slider form factor is becoming increasingly common on the mobile market - many handsets come both with a numerical and a QWERTY keyboard. For instsnce, the downslide numerical keypad and the sideslide QWERTY keybard are combined in the Samsung SGH-F520 PDA phone. Nokia are advancing even further by patenting a triple slider. The development goes by the name of "A layered mobile device" - and effectively is a multi-layer handset.

The concept provides for a sliding QWERTY keyboard that exposes the numerical keypad if moved downwards or the player controls if moved upwards (having something in common with Nokia N95). The secondary QWERTY-keyboard can be reached by sliding aside. In such a fashion, you can have two QWERTY keyboards availale at the same time.

It remains unclear though if this form factor will be utilized for any of the planned Nokia phones in the nearest future. The idea, however, is perfect: supplying a mobile device with a system of controls that can challenge that of a PC. A touchscreen would make a perfect addition to this system as well. On the other hand, the compactness is sacrificed, and the mechanism is going to be overly complicated.