SOME of the difficulties overcome by the British Broadcasting Corporation in establishing a broadcast service between Great Britain and distant regions of the Empire are well described in a paper in Electrical Communication of April by C. M. Benham and P. H. Spagnoletti. Except in special cases, long distance radio communication is practical only when short wave-lengths are used. It was necessary therefore to use radio equipment of the short wave type. Fortunately, the colonies and dominions are so distributed longitudinally that they can be conveniently divided into time zones, that is, areas which have approximately the same local time. There are four main zones: Australia, which has a time displacement relative to London of ‘eight hours early’; India, ‘four hours early’; Africa, the same time; and Canada, ‘six hours late’. In the case of Australia, the farthest away, transmission must travel through twilight conditions whichever path round the world is used. It was not expected therefore that wave-lengths of 15 metres, using the daylight path, or 37 metres using the dark path, would give trustworthy service. Both can be used for short periods but their useful duration is limited arid uncertain. The twilight band (25-29 metres) has been found to be the best. In the Indian zone it has been found that 17 metre transmissions are very satisfactory. In the case of Africa, as it lies almost due south, shorter wave-lengths are used during the day, intermediate wave-lengths at dusk and at night-time 32 metre wave-lengths or even longer can be used. It is found better to divide Africa into two zones. The great circle path to Canada passes very near to the north pole and even in summer it is not a true daylight path. A satisfactory day wave for Canada is of the order of 19 metres, but night waves of 31 and 50 and sometimes as high as 70 or 80 metres have been used. The B.B.C. deserves great credit.for having overcome so successfully many of the difficulties connected with the most ambitious project ever attempted in broadcasting.