RADIO SIGXAUNG SYSTEM 537 



corresponds to the code setting of a particular selector, it will be 

 advanced step by step until it reaches the point at which it makes 

 signaling contact. For any other signal, however, it will be released 

 at the pause between some two groups of pulses and will then im- 

 mediately fly back to its initial position. To hold the code wheel 

 during signal pauses a series of pins is arranged to engage a spring 

 arm on the selector frame, their position thus determining the code 

 of the particular selector. As the master key can be so operated as 

 to send signals without any pause a general call can be made through 

 all selectors simultaneously whatever their code setting. When the 

 code wheel has rotated a distance corresponding to twenty-seven 

 impulses, a spring contact mounted upon it makes contact with the 

 first of a series of four stationary contacts A, B, C, and D. Two more 

 impulses make contact with the second of the series, two more with 

 the third, and two more, or a total of 33, with the fourth. Only one 

 of these contacts is connected in any individual selector and four 

 large groups are thus provided. All the transmitting keys are so 

 arranged that about one second after the completion of their calling 

 signal, they send a signal which restores all selectors under their 

 control to normal. 



By omitting one or both of the pauses between the three groups of 

 impulses, it is apparent that each selector will respond to four and 

 only four systems of pulses for each contact. On contact A, for ex- 

 ample, the selector will close the signaling circuit if its individual call 

 is sent, if the first pause only or the second pause only is omitted, or 

 if both pauses are omitted and 27 consecutive impulses are sent. 

 All of the selectors using any one of the four contacts may thus be 

 grouped in several different ways. The total possible number of 

 individual stations in each of the four large groups is somewhat over 

 200, or over 800 in the entire system, the exact number depending 

 upon the grouping system which is employed. Each large group 

 may be subdivided into a number of small groups having from 15 to 

 20 stations in each group, of which each station may belong to two 

 groups if desired. In any case the number of consecutive impulses 

 without pauses corresponding to the contact used will call all the 

 stations in that large group, the sub-groups being formed by omitting 

 one of the pauses. The system is thus capable of a high degree of 

 flexibility. 



The operation of the selector closes a circuit through the winding 

 of a relay. This relay is of the slow operating type, this being neces- 

 sary in order to avoid signals due to momentary contacts which are 

 made by the selector with certain code combinations. The relay is 



