The diagram in Figure 140 shows how the relay is connected to a telegraph line. How To Learn To Telegraph The instruments so far described have been practical working telegraph instruments, but they lack the fine points of commercial apparatus and it is not possible to become as efficient an operator with their aid as with a real key and sounder. If the young experimenter desires to become a proficient telegraph operator, the first thing to do is to purchase a Learner’s telegraph key and sounder. Connect a dry cell to the binding-posts on the back of the instrument. Screw the set down on a table about eighteen inches from the front edge, so that there is plenty of room for the arm to rest. See that none of the various adjustment screws about the instrument are loose and that the armature of the sounder moves freely up and down through a distance of about one-sixteenth of an inch. The spring which draws the lever upwards away from the magnets should be set only at sufficient tension to raise the lever when no current is passing. If too tight, the spring will not allow the armature to respond to the current flowing through the magnets. The key is provided with several adjustment-screws to regulate the tension and the play of the lever to suit the hand of the operator. A little practice will enable the student to judge best for himself just how the key should be set. The next step is to memorize the alphabet, so that each character can instantly be called to mind at will. The punctuation marks are not used very frequently, and the period is the only one which the student need learn at first. The Morse alphabet consists of dots, dashes, and spaces. Combinations of these signals spell letters and words. Many of the characters are the reverse of others. For example, _A_ is the reverse of _N_. _B_ and _F_, _D_ and _U_, _C_ and _R_, _Q_ and _X_, _Z_ and _&_, are the other reverse letters, so if the formation of one of each of these letters is memorized the reverse is easily mastered. It is important that the beginner should learn how properly to grasp the key, for habits are easily formed and a poor position will limit the sending speed of the operator. Place the first or index finger on the top of the key-handle, with the thumb under the edge; and the second finger on the opposite side. The fingers should be curved so as to form a quarter-section of a circle. Bring the third and fourth fingers down so that they are almost closed on the palm of the hand. Rest the arm on the table in front of the key and allow the wrist to be perfectly limber. [Illustration: Fig. 141.—How to hold a Telegraph Key.]