A decoupling capacitor is formed in a semiconductor substrate that includes a strained silicon layer. The first engagement means being connected to the second engagement means via at least one first joint being in form of a pivot andor at least one first spring means in order to be at least partly displaceable relative to the second engagement means, and a method using such a tool. The telephone line interface is coupled to a telephone line to apply the telephonic data signals to and receive signals from the telephone line.