Page:Popular Science Monthly Volume 88.djvu/810

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��Popular Science Monthly

��Tubular Quenched Gap

��A PATENT for a novel form of quenched spark-gap is No. 1,132- 589, issued in 1915 to F. H. Kroger. In the illustration is shown one of the diagrams forming part of this patent. The gap units are made up in groups of two sparking spaces connected in series, and each unit slips into a pair of clips much as does an ordinary cartridge fuse. This gives complete interchangeability and makes it possible to substitute new gaps for any which happen to break down,

���Interchangeable gap units for a tubular quenched gap

without disturbing the sections which re- main in useful condition. As may be seen from the illustration, each unit has as its most important parts the central tube 10 and two shorter cylinders 6 and 6a, which slip over the inner tube with a small space between them and which have their ends expanded to a consider- ably larger diameter than their central portions. The outer tubes are supported by the grooved insulating disks 7, which serve also to hold them con- centric with the inner cylinder 10. Between the end supports and at the extremes of the units are placed soft rubber washers 8, and the entire struc- ture is clamped between washers and the nuts 9, so as to form a rigid, air- tight assembly. The spark passes between the inner cylindrical surface of the cylinder 6 and the upper, outer and parallel surface of 10, and, after the current traverses tube 10 to its lower portion, it passes from the lower outer surface of 10 to the inner and parallel surface of 6a. The current is then led to the second unit through clip 4c, and jumps two more gaps. As many gaps may be placed in series as needed. The spacing between sparking surfaces re- mains constant regardless of the pressure on the gaskets.

��An Unusual Recording Receiver

IT has been known for many years that a wireless telegraph power trans- former connected directly to lighting of power lines would often set up, in those supply circuits, very severe disturb- ances. Unless proper protective meas- ures are resorted to, it sometimes happens that the operation of a wireless telegraph transmitter thus connected will cause sparking, insulation break- downs and other troubles at some distance from the sending station. In a plan disclosed in U, S. patent No. 1,143,799, issued during 1915 to R. B. Avery, these line disturbances are made use of to record or make evident the operation of a wireless transmitter. Referring to the figure, it is seen that the primary 2 of a step-up transformer I is connected to the alternating current power lines 3. One terminal of the secondary coil 5 is led to the adjustable spark-gap 6 through wire 4, and the circuit passes thence through wire 9 to

���System for recording messages received by power lines

the swinging plate of a special condenser, 10. The other plate of this instrument, 8, connects through 7 with the second- ary coil and is separated from 10 by the insulating sheet ii. The pivoted sheet 10 is mechanically connected through 21 to the contact apparatus 12, which comprises a lever 19, moving and fixed contacts 18 and 15, and an adjusting spring 17, as shown. When this contact is closed, current flows from battery 25 through the local lines 22, 23, and the sounder or recorder 24 is operated.

In using this receiver, the spark-gap 6 is opened just beyond the point where

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