An umbilical probe sensing system is described which includes an automated system for accurately obtaining physiological information from an infant in real time. The retarder 5 has regions 8 and 9, at least one of which alters the polarisation of light from the input polariser 4. In addition, a method for such a fuel cell includes passing a reactant into an entry port of the first field and out of an exit port of the first field, mixing the reactant with a fresh reactant so as to form a mixture, and passing the mixture into the entry port of the second field. Annual entries can be defined and allocated during the calculation phase into corresponding primary entries. The mating end is configured to be electrically connected to an electrical component.