S. W. Lindsay

Most wireless telegraph receivers are complicated, expensive and somewhat speculative, the results from them depending very materially upon one's skill and experience. Only a small percentage of the receivers produced by the more prominent wireless companies properly perform the service intended of them ; but the instrument described below is simple, cheap and positive in its workings.

Mounted by means of tin straps on a base of wood, 6" x 10 1/2" x 1", is an ordinary dry battery, at each terminal or pole of which is a double screw binding post. Each of these binding posts carries a stick of carbon in its upper hole, about 1/8" in diameter and 1 1/2" long, converging slightly. The lower hole of one post is connected with the carbon of the battery by a piece of neatly-coiled wire, leaving the zinc and the lower hole of the other binding-post free to make connection with the telephone receiver.

One and one-half inches from each of these binding posts and connected with them by a stout wire (which may be placed in a groove and is screwed down under the posts) is a single wood screw binding post. The screw on the telephone side is for the earth connection and the other is for the air wire, or atennae. The principle of the instrument is, as in other receivers, imperfect contact of conductors. In this instance it is formed by a highly polished piece of steel, such as a needle, resting against the carbons. There are two methods of supporting the needle. One is by a spring of light tension hung from a bent wire support as shown in the photograph. The spring can be made by turning brass wire around a pencil or small round stick. The other method is to bore a small hole in (but not through) each carbon, placed so that they point towards each other. Then between them the needle is fixed the ends resting in the holes mentioned. The needle thus makes a slight but firm contact.

When all are assembled the circuit is completed through the telephone receiver in which the signals are made audible as buzzes, the long ones being dashes, the short ones dots. Superior results can be obtained when the ocillation at the spark gap of the sending apparatus is very rapid, spreading waves in rapid succession. The reading of the signals, either in the American or Continental Morse Code, is simple, and with but little practice any one can take messages easily and accurately.

Compared with other receivers tested by the writer, the one described above is the most satisfactory because of its reliability and simplicity. Under conditions where all others would cease working and demand re-adjustment, it remained the same for days at a time. Beside, it admits of much handling, and works immediately upon being set up, catching the first signals clearly.