ALL large passenger ships have a complete staff of radio operators and keep a continuous watch for radio signals. The great majority of ships, however, have only one radio operator, and so a continuous watch is impossible. Such a ship might be in close proximity to a ship needing assistance and hear nothing of its distress calls. Probably a much larger ship at a greater distance away would be diverted from its course to give the requisite assistance. This would lead to delay and greatly increase the cost. This difficulty has now been overcome by the apparatus designed by the Marconi International Marine Communication Co., Ltd. The object of this auto-alarm is to ensure that the call shall be received by the smaller ships even when the operator is off duty. The alarm signal consists of a series of three dashes, each of four seconds duration, separated by intervals of one second. The Post Office regulations insist that this signal, the forerunner of the distress (S.O.S.) call, shall operate the receiving apparatus, which rings a bell to recall the operator, even when it is sent by hand with the aid of an ordinary watch with a seconds hand. If the signal be wrongly sent, even although the apparatus is set in motion, it will instantly come back to zero and be ready to receive signals correctly sent. Allowances are made for want of skill of the operator by making it operate when the dashes have intervals between three and five seconds long arid the blanks have intervals lying between one fifth and two seconds. The apparatus operates even when two ships are sending Morse messages at the same time and on the same wave-length. When a distress call is received, alarm bells are rung on the bridge, in the radio cabin, and in the operators' sleeping quarters.