Inspector of Machinery (Electrical], Royal National Life-boat Institution.

ViTH the exception of seven short- range boats, all the Institution's life-boats, both in the active and in the active reserve fleet, are equipped with radio telephony. The advan- tages of a life-boat being in two-way communication with the shore during a service are many. The coxswain can be given the latest information about the position and condition of the casualty; he can advise the station of the number of survivors picked up and arrange for medical aid and ambulances if necessary; and the life- boat can be recalled if the vessel for which she is searching succeeds in reaching shelter. This last advantage is greatly appreciated by the life-boat crew, who might otherwise continue searching unnecessarily.

While on service, all distress mes- sages are passed on the international distress frequency of 2182 kilocycles (137.5 metres). This traffic is handled by the nearest G.P.O. or Coastguard radio station, and all other traffic is kept off this frequency until the life- boat's service is completed or the distress call cancelled.

Simple to Operate The radio-telephones, which are now fitted as standard equipment, were designed and manufactured especially to meet the Institution's requirements by Messrs. Coastal Radio, Ltd., of Edinburgh, who install and service the equipments on a hire-maintenance basis. The number of sets fitted is 164, and the annual cost to the Institution is between £9,000 and £10,000.

The equipment must be, and is, simple to operate and reliable, and it has to be stowed into as small a space as possible. It is divided into five separate units, the transmitter, the receiver, the power pack, the remote control panel and the loud hailer projector. In the larger life-boats the first three units are installed in the cabin, but in the smaller types they are fitted into watertight boxes on either side of the deck. The remote control panel is alongside the engine room instrument panel, -within easy reach of the life-boat's motor mechanic who usually acts as radio operator.

The loud hailer projector is mounted in a convenient position on the deck.

The transmitter contains six valves and is crystal-controlled. It can operate on any of four pre-set frequen- cies, selected by a five-position switch which is the only control on the trans- mitter panel. The fifth position feeds the output from the amplifying stages directly into the loud hailer, which can be heard clearly at distances up to four hundred yards.

Superheterodyne Receiver The receiver also uses six valves and is of the superheterodyne type. A click-stop mechanism on the tuning control enables any one of five pre- determined frequencies to be located and held. The only other knob is the volume control.

The remote control panel has its own microphone, loud speaker and volume control, on/off switches for the transmitter and receiver and a switch to bring the loud hailer into circuit when required. The same microphone is used for both transmitting and hailing. Headphones are also pro- vided.

The power pack is fed with current at 12 volts through a changeover switch from either the port or star- board battery. The low tension cur- rent passes direct to the valve heaters, and the high tension current is pro- duced by two rotary generators. The smaller of these supplies the receiver and is running the whole time the life- boat is at sea. The larger supplies 475 volts for the transmitter and comes into operation only when the switch on the microphone is pressed to transmit a message or use the hailer.

The current taken from the boat's batteries is 6 amps while the receiver is working and the transmitter is in the stand-by position, and 19 amps while actually transmitting or while the hailer is in use.

Heard 550 Miles Away The output from the transmitter varies with the type of aerial used; with a whip aerial, it radiates about 18 watts and with a twin wire aerial about 30 watts. The reliable range of the equipment is about 100 miles, but the range is to some extent dependent upon land screening and the type of aerial used. Some remark- able results have been reported from time to time. Signals from the Court - macsherry (Co. Cork) life-boat have been received at good strength at Fraserburgh (Aberdeenshire), a dis- tance of 400 miles, and the Cromarty life-boat has been heard in the Scilly Isles about 550 miles away.

Direction finding equipment has been fitted experimentally to four life- boats stationed at carefully selected points, i.e. Rosslare Harbour in Eire, Aberdeen in Scotland, Ramsgate in England and Holyhead in Wales.

This equipment enables a life-boat to take bearings on and set a direct course to a casualty, provided of course, that the casualty is also equipped with radio-telephony and is able to trans- mit. A loop aerial is fitted above the deck cabin and a goniometer unit installed alongside the radio equipment.

The direction finding equipment works in conjunction with the existing receiver and was designed by Messrs.

Coastal Radio, Ltd., at the Institu- tion's request.

The Institution keeps under con- stant review the latest inventions and developments in such fields as those of radar, echo-sounders and navigator equipments, but up to now these have not been found suitable for the special purposes for which life-boats are needed..