Populor Science Monihly 



377 



quarter revolution the distributors con- 

 nect on the Hne four operators using one 

 duplex "channel" set, which consists of 

 a sender and receiver at each end. 



The operation of the two distributors 

 is perhaps the most important new thing 

 in this system, since it is through them 

 that the line can be used successively by 

 each of the four groups of four oper- 

 ators. The simple fact that in printing 

 telegraphs over three-cjuarters of the to- 

 tal time of operation is used for prepar- 

 ing to send, and in printing the letters, 



plished in one-tifth of a second, and dur- 

 ing each quarter of this period, or one- 

 twentieth of a second, each set of in- 

 struments is connected to the line. In 

 the three-twentieths of a second the re- 

 ceiving printer operates and the trans- 

 mitter prepares to send the set of five 

 impulses corresponding to the next letter 

 in its message. 



The other photograph shows the eight 

 operators, four sending and four receiv- 

 ing, who work at one end of a trunk line 

 using this new c[uadruple-duplex printer. 



The problem of bridging a mountain stream, circling the edge of a precipice and "tacking" 

 up a steep grade forced the engineers responsible for the electric railway up Mt. Lowe to 



make this queer "circular bridge" 



while less than one-quarter will suffice 

 for the actual transmission of the five 

 electrical impulses, has made possible 

 this distribution and simultaneous op- 

 eration. The distributors are merely 

 special rotary switches which revolve, 

 one at each end of the wire, at exactly 

 the same efifectixe speed. For each 

 quarter revolution the duplex line is con- 

 nected to one set of instruments and 

 the impulses forming one letter are 

 transmitted in both directions. If the 

 distributor rotates at three hundred rev- 

 olutions per minute, three hundred let- 

 ters or fifty words per minute will be 

 sent in each direction through each of 

 the four channels, making a total of 

 four hundred words per minute. Each 

 revolution of the distributor is accom- 



A Circular Bridge on Stilts 



THE circular bridge shown in the il- 

 lustration is unusual both in its de- 

 sign and in its location. The trestle 

 work forming almost a complete circle, 

 practically all of which is "on stilts," is 

 a part of a mountain inclined road. At 

 the point where the roads almost meet, 

 one track is about six feet higher than 

 the other. The circle formed by this 

 track is seventy feet in diameter. 



This bridge is also noteworthy be- 

 cause it is located nearly five thousand 

 feet above sea level. It is a portion of 

 what is known as "The Mt. Lowe in- 

 cline railway," a line which winds its 

 way up the side of Mt. Lowe. The turn 

 seems to show how crooked is this three- 

 mile line. 



