82 BELL SYSTEM TECHNICAL JOURNAL 



Fundamentally this switch consists of three major functional parts: 

 (a) twenty separate vertical circuit paths, {h) ten separate horizontal 

 circuit paths, and (c) a mechanical means for connecting any one of 

 the twenty vertical circuit paths to any one of the ten horizontal 

 circuit paths by the operation of electromagnets. From a structural 

 viewpoint the switch is comprised of a rectangular welded frame on 

 which are mounted twenty vertical units and the selecting mechanism 

 consisting of five horizontal bars operated by ten selecting magnets. 



Primarily the switch is a multiple relay structure with twenty 

 vertical relay-like units, each unit having an operating or "holding" 

 magnet and ten sets of contacts in a vertical row. The switch arrange- 

 ment provides a rectangular field of contacts in twenty vertical rows 

 and ten horizontal rows or a total of 200 sets of contacts, one set at 

 each "crosspoint." These crosspoint contacts are operated inde- 

 pendently of each other by a coordinate operation of the horizontal 

 and vertical bars. The horizontal bars are controlled by the ten 

 horizontal or "selecting" magnets and the vertical bars by twenty 

 vertical or "holding" magnets. Any set of contacts in any vertical 

 row may be operated by first operating the selecting magnet corre- 

 sponding to the horizontal row in which the set of contacts is located, 

 and then by operating the holding magnet associated with the vertical 

 row. Since the contacts are held operated by the holding magnet 

 alone, the selecting magnet is operated but momentarily and is 

 released as soon as the holding magnet is operated. After the selecting 

 magnet is released, other connections may be established through the 

 switch by the operation of other selecting and holding magnets. It is 

 thus apparent that ten connections can be established through the 

 switch, one for each of the horizontal paths. 



From Fig. 2 the rather simple mechanical interlocking of the 

 horizontal and vertical bars which causes the operation of a set of 

 crosspoint contacts will be understood. The ten sets of contacts in a 

 vertical row are associated with the vertical or "holding" bar of the 

 row. Each horizontal or "selecting" bar is provided with twenty 

 selecting fingers which are made of flexible wire. These fingers are 

 mounted at right angles to the bar, one at each of the vertical rows of 

 contacts. Thus when a selecting bar is rotated through a small arc 

 by its magnet, the selecting fingers will move up or down into a 

 position so that when a holding bar is operated by its magnet, it will 

 engage the selecting finger at the crosspoint of the two bars and cause 

 the corresponding set of contacts to operate. The selecting bar and 

 the fingers not used will then be released when the selecting magnet 

 is released, but the selecting finger used to operate the selected set of 



