A roller ball pen for use with metallic inks, and a method for assembling the roller ball pen for use with metallic inks, is described herein. A first receive power measurement is obtained at a second node with a controlled optical source at a first node turned on and with a plurality of Raman pump lasers at different wavelengths at the second node turned off. In order to provide a cost-effective and easy-to-install gear-changing device, the bolt is held by a catch. An adhesive backing is provided for attaching the timer device to the container. The mobile communication device prevents a part of light emitted from an optical source from being displayed on a screen with a high brightness. The frequency offset is estimated based on a conjugate product between received symbols across at least one pair of multi-carrier symbols of each of the pilot sub-carriers of the selected subset of the plurality of pilot sub-carriers.