Patent ID: 8223994

Claim:
A method of limiting the maximum permitted sound volume in an earphone, a headset or the like, where a driving signal for driving the earphone or the headset has a voltage that is less than approx. 0.7 V, the method including the steps that: the size of the driving signal is sensed and that, on driving signals exceeding a certain level, a part of the driving signal is shunted past the earphone or headset, characterised in that a second part of the driving signal is diverted and supplied to a unit comprising a detector device and a shunt device, in which the shunting of the first part of the driving signal takes place, and that the unit is given a sensitivity to operate at voltages of less than approx. 0.7 V, characterised in that an MOS transistor included in the unit is provided with an insulation layer between its gate and silica based substrate of reduced thickness and/or higher dielectricity constant.