A method of operating a touch panel using a controller, the touch panel comprising: a first conductive pattern having first and second ends on a first layer; a second conductive pattern having first and second ends on a second layer; the second conductive pattern being electrically coupled to the first conductive pattern via a contact resistance Rt, wherein the contact resistance Rt varies in dependence on a force applied to the touch panel and is much greater than the resistance of either the first or second conductive patterns; the method comprising acts of: (i) determining a second resistance Rx across the first and second ends of the first conductive pattern; (ii) whilst applying a first predetermined voltage Vcc across the first end of the first conductive pattern and the second end of the second conductive pattern, determining a first voltage V1 at the second end of the first conductive pattern and determining a second voltage V2 at the first end of the second conductive pattern; (iii) whilst applying a second predetermined voltage across the first and second ends of the first conductive pattern, measuring a third voltage Vx- at the second end of the second conductive pattern; determining a value of the contact resistance Rt as a function of the first voltage V1, the second voltage V2, the third voltage Vx- and the second resistance Rx; and producing a control signal based on the determined value of the contact resistance Rt. a first conductive pattern having first and second ends on a first layer; a second conductive pattern having first and second ends on a second layer; the second conductive pattern being electrically coupled to the first conductive pattern via a contact resistance Rt, wherein the contact resistance Rt varies in dependence on a force applied to the touch panel and is much greater than the resistance of either the first or second conductive patterns; the method comprising acts of: (i) determining a second resistance Rx across the first and second ends of the first conductive pattern; (ii) whilst applying a first predetermined voltage Vcc across the first end of the first conductive pattern and the second end of the second conductive pattern, determining a first voltage V1 at the second end of the first conductive pattern and determining a second voltage V2 at the first end of the second conductive pattern; (iii) whilst applying a second predetermined voltage across the first and second ends of the first conductive pattern, measuring a third voltage Vx- at the second end of the second conductive pattern; (i) determining a second resistance Rx across the first and second ends of the first conductive pattern; (ii) whilst applying a first predetermined voltage Vcc across the first end of the first conductive pattern and the second end of the second conductive pattern, determining a first voltage V1 at the second end of the first conductive pattern and determining a second voltage V2 at the first end of the second conductive pattern; (iii) whilst applying a second predetermined voltage across the first and second ends of the first conductive pattern, measuring a third voltage Vx- at the second end of the second conductive pattern; determining a value of the contact resistance Rt as a function of the first voltage V1, the second voltage V2, the third voltage Vx- and the second resistance Rx; and producing a control signal based on the determined value of the contact resistance Rt.