But apart from such carefully prepared devices the men of the Royal Engineers are past masters in the art of rigging up, according to the conditions of the moment, all sorts of makeshift apparatus whereby signalling over quite long ranges can be carried on by "wireless." Such improvisations, could they be recorded, would constitute war inventions of a high order.
CHAPTER XXII
MILITARY TELEGRAPHY
Telegraphy plays a very important part in warfare. The commander of even a small unit cannot see all that his men are doing or suffering, but is kept posted by telegraph or telephone, while communication between units depends very largely indeed upon such means. Wireless telegraphy, in land warfare, is largely devoted to communication between aircraft and the artillery batteries with which they are working, and to avoid interference with that important work telegraphy by wire is employed for most other purposes.
Right at the front this communication is kept up by means of that type of instrument which the soldiers call a "buzzer," for the good and sufficient reason that that is really what it does.
In view of the fact that soldiers speak of their home-land, for which they are enduring all manner of risk and hardship, and to which they are longing to return, by the contemptuous-sounding name of "Blighty," we might expect that what they call a buzzer has nothing whatever to do with making sound, but in this case the name describes the thing very aptly. Its sole purpose and intent is to make buzzing sounds of either long or short duration.
Perhaps the simplest way in which I can describe this useful and interesting invention is by telling you how you can make one for yourself. It is nothing more than an electric-bell mechanism connected up in a certain way.
As most people know, an electric bell contains a magnet made of two round pieces of iron placed parallel and yoked together at one end by means of a third piece of iron, generally flat, while on to each round piece is threaded a bobbin of insulated wire. The iron becomes a magnet when, and only when, current flows through the wire.