A method and system for duobinary coding of optical signals, wherein a precoded duobinary signal is supplied to a phase modulator which converts it to a phase-modulated optical signal, an optical filter carries out the function of the coder and converts the phase-modulated signal to an optical duobinary signal, and the duobinary coding results in a reduction in the bandwidth. The portable cellular communication device can direct the user to a parked vehicle utilizing location data of the portable cellular communication device provided by a GPS transmitter or a wireless node, and current vehicle location information provided by accessing a vehicle location database. The EC manager module may then adjust operation of at least one hardware element to keep operation of the PCD below the calculated instantaneous electrical current level for the PCD. At least one magnet is installed into a rotatable actuator in proximity to the surface of the sensors whereby the magnetic field generated by the magnet causes the corresponding sensors to switch to an open position when at least one magnet is in their proximity.