234 



POPULAR SCIENCE MONTHLY 



contact plug, which can be moved on the vertical bars, and when placed over one 

 of the horizontal bars, springs into firm contact with it . . . (as shown in Fig. 

 11). The brass rods for connecting any two lines together are fastened to the 

 walnut frame, and in front of them but not touching, are the upright rods. 

 The line circuits, as they enter the office, are connected to the upright rods 

 by binding screws on top of the frame. Each of the upright rods has a 

 spring-slide which, when pulled outward, can be slid freely on the rod, and 

 which, on being released, springs into firm contact with any one of the hori- 

 zontal rods with which it may be desired to connect it. 



Within a year the increase in the number of subscriber-lines in the 

 New Haven exchange made an additional board necessary. So a 

 Snell board having a capacity for thirty-five subscriber-lines was in- 



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Fig. 12. 



Fig. 13 



stalled and connected to the old board. The principal feature of the 

 Snell board (Fig. 12) is the Snell jack (Fig. 13). The instructions 

 sent with the board read : 



The line connects the levers together perpendicularly. The springs being 

 connected horizontally, form the connecting bars. Any two circuits are con- 

 nected by throwing the corresponding levers on the same row of springs. We 

 have testimonials from parties using the switch, where one operator does all 

 the work satisfactorily for three hundred subscribers, where with any other 

 system it would require at least two, thus making a permanent saving in the 

 running expenses. 



A cheaper type of Snell switchboard is shown in Fig. 14, using what 

 are called ' tip-up jacks.'" This board consisted of an 



inclined table, having as many grooves, about a quarter of an inch wide and 

 deep, as may be required for connecting bars. Between every third groove is 

 a row of counter-sunk holes for the wire posts inside of a spiral spring; a 

 smaller wire passing through the ends of the posts forms the line and acts as a 



