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. Near the free ends of the round pieces, or the poles of the magnet, to use the orthodox term, is placed another little piece of iron called the armature, carried upon a light spring. When the current flows in the wire the armature is pulled towards the poles against the force of the spring, but when the current ceases the magnet lets go and the armature, urged by the spring, swings back again. Behind the armature is a little post through which passes a screw tipped with platinum, and in operation this screw is advanced until its point touches a small plate of platinum carried by the armature. Connection for the current is made to this "contact screw" whence it passes to the armature, through the spring to the wire upon the magnet, through that and away. On completing the circuit, then, as when you push the button at the front door, current flows and energizes the magnet. A moment later, however, the armature moves, breaks the contact with the screw and stops the current. Then the magnet lets go and the armature springs back, making contact once more and setting the current flowing again. These actions repeat themselves over and over again quite automatically, and the hammer which is attached to the armature vibrates accordingly. That is the ordinary familiar electric bell. Cut off the hammer and you have a buzzer with which excellent telegraph signals can be sent. So much for the sending apparatus. The receiving device is simply an ordinary telephone receiver. There is sometimes a little confusion in people's minds because of this. A telephone is used, but it is used as a telegraph instrument. The sounds heard in it are not speech but long and short buzzing sounds which, being interpreted according to the code of Morse, deliver up their message.