Page:Popular Science Monthly Volume 90.djvu/643

 �e Amateur - Eloctrician

��T^nd Wii'eless Operator

��Delicate Recorder for Wireless Telegraph Signals

PROF. TURPAIN, a prominent Parisian scientist, has been engaged for some time past on the subject of recording instruments for wireless waves, and has brought out a very sensitive recorder which is intended for long-distance % wireless working, and which will take down signals so weak that ordinarily they could only

���A sensitive recording device for receiving signals too weak to be heard in a receiver

be heard in the telephone. The device con- sists of a powerful permanent magnet M of the type used for ocean cable work, with a flat swinging coil A, mounted on the fiber suspension B. On the coil is a light arm C which connects by a thread D to the recording device, so that the slight move- ments of the coil will produce larger move- ments of the pen. The recorder consists of a swinging arm E which is pivoted at F in the usual way. The lower end of the arm carries the pen P. Under the pen, but without touching it, passes the paper band H mounted on the rollers G. The novel part of the invention consists in making the record without having the pen touch the paper, for this would cause too great a friction for the small amount of pull afforded by the swinging coil. The pen contains a volatile liquid, such as ammonia, and the vapors of this substance are made to act on a paper that is moistened with a uitable chemical preparation so that the

��ammonia v^apor will produce a color upon the paper. Certain compounds of phenol can be used for this purpose. When the paper travels along and the pen operates, the signals will be recorded in a wavy line corresponding with Morse dots and dashes.

��A Self-Contained Battery Lamp for Physicians' Use

THE illustration shows an improvement over the usual kind of batter>' lamps which physicians or surgeons use for ex- amining the eye or the mouth. Generally the battery- is carried in the pocket, but the flexible cords often become tangled. Besides, where a contact device is used for the lamp, the hands should be left free. In the device shown, the entire outfit is carried on the head and is self-contained. A suit- able head-strap holds the battery-case, and the electric lamp is held ver>' conveniently on the under side of the box. The lamp- holder with its lens is mounted so as to swing on a piv- ot, and a rack- pinion operated by a milled head provides a way to throw the beam up or down. A flexi- ble cord leads to a spring con- tact which is carried in the mouth, so that contact can be made by the teeth for light- ing the lamp. This device leaves the operator's hands entirely free and eliminates the bother encountered with the cords of the pocket lamp.

���Battery and light strapped on forehead

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