an object; or (b) the detection of an object;; by means of the constant velocity or rectilinear propagation characteristics of Hertzian waves. Ship station means a radio station installed in a vessel which is not permanently moored. Special service station means a radio receiving station used exclusively for the purposes of receiving time signals, notices to navigators, epidemiological and medical advice and like services of general utility. Standard frequency means a radio transmitting station used for the purpose of transmitting standard and specified frequencies of known high accuracy intended for general reception. station 46