Page:Popular Science Monthly Volume 91.djvu/336

This page needs to be proofread.


��Popular Science Monthly

��Holding the Morse Key

��Having mounted the key, the next thing to learn is how to hold it properly. There are variations in the "grip" from operator to operator, but the essentials are that the fingers should be arched into an approx- imate quarter circle and have their tips resting on top of the knob, the thumb should press gently but firmly on the side- rim of the knob, the wrist should be held up clear of the table surface and the elbow should rest upon it. The key should be pressed shut, never "tapped," and should open easily through the action of its own spring. The muscular impulse which closes the circuit must be gentle and firm, coming from the full arm. The wrist must not be stiff, nor yet must the lower arm muscles be used (through the wrist-joint) for the entire key manipulation. The proper dis- tribution of muscular effort, and the cor- rect use of the inertia of the fore-arm for rapid sending can only come from long practice; nevertheless, it is important to bear the above suggestions in mind at first, so as to form correct habits at the beginning of work.

Practicing Dots and Dashes

The first actual sending should consist of dots only. Make dots slowly, being careful to keep the interval between each pair of them exactly the same length as the dots themselves. As you find that you can make them perfectly, increase the number until you can send three or five per second without difficulty. Then take up dashes, slowly at first, increasing the speed till about one per second can be made perfectly. Remember that when sending dashes the space between each pair of signals must be only one third as long as the dash itself; this is the only difference between the rapid series of dashes and the slow series of dots. Next take up alternate dots and dashes, being careful to keep the spaces between the signals correct. Although speeds corresponding to those suggested must be attained through practice, never sacrifice accuracy for the sake of sending fast. Reliable, smooth and carefully-spaced transmission is the first requisite; speed follows as a matter of course.

When the student overcomes the difficulty of changing from dots to dashes by prelimi- nary practice of the sort just described, he may begin sending Morse letters and words.

��The first two groups of letters (Fig. 2) and the practice words given here will afford ample work for some time. As soon as the first six letters are thoroughly learned, the third group may be used. New practice words and sentences may now be made up easily, since the fourteen letters using three or fewer signals permit spelling a large number of words. At this stage of practice it is advisable to commence reading by sound. Consequently an auto- matic sender or a companion student is needed. In the next article, circuits for a buzzer telegraph line, over which messages may be sent between two houses or rooms, will be described. Meanwhile learn and practice the code, and remember that care and accuracy are the two essentials for which to strive.

(To be continued)

���A Fixed Adjustment Detector Easily Made at Home

A SIMPLE "permanent" detector is constructed of materials found in al- most every experimenter's workshop.

Secure a piece of mica j4 in - square. Next, select a piece of sensitive galena. It should not be larger than a B-B shot. Cut a hole, just the shape of the galena, only slightly smaller, in the center of the square of mica. Push the galena half way through the hole and fill up the cracks between the galena and mica, with glue. Be careful, how- ever, not to get any glue on either protrud- ing face of the crystal.

While waiting for the glue to harden, remove the two thumb-nuts from the bind- ing posts on any ordinary dry battery. Glue these nuts, top outwards, to each side of the mica so that the galena will be between the burrs but touching neither of them. After the glue is dry the projecting mica may be cut away.

Pour fine brass-filings in on either side of the galena and screw in on either side a brass bolt taken from a dry battery.

The whole is then mounted on a suitable base and held in place by spring clips. This detector may be easily adjusted by simply tightening or loosening the bolts as desired. — Edward M. Weyer, Jr.

��Filings in nuts be- tween the bolt ends

�� �