Ri'.i.iys /.v ////; mil. I. s) si i.m 21 



str|)|)ini; swilrh m.ii;iK't (>i)i'ialr> the --wihli .iniuii iiic ,iiul holds il 

 ill a position to aihaiu't.' tin- switcli a siiij^li' sUp when llu- inaL;nft is 

 ri'liMscd. W'lu'ii the dial ronlarls closi' tlic ( iniiii ,ii;.Liii llu' [)iilsf 

 irla\' ri'-operates, rck-asiiiv; llu' strppiiii; swiicli. wliich adxanct-s one 

 sti'p, and rt'ostablishins tin- riniiit Inr the slow -nlt-ase relay. This 

 i\clc is repealed for each hriak .mil m.ikc piiUr period in order to 

 advance the stepping; switch o\ er the niinilHi' nl irrniin.ils correspond- 

 ing to the digit dialed. 



The adjustnieiU of substation dials is such that |)ulses are sent at 

 a rate of speed of not less than einht, or more ih.m IweKe pulses per 

 second. The break period of iiulix idu.il i)ulses ma\ \-,uy Irom .045 



10 th 

 Step 



'^s'-STl^^liJl^T^JlirilJTiniJllITii^^^^^^'^' 



n 



1 Switch Relay Resistance 



Slow Release Retey 



Puhe Relay 



i SubsUrtKwLoopj— ^ 



Fis. 1-4 — t.'iir\e shuwint; inilsiiig impulses 



to .100 second and the make period may \'ary from .025 to .050 

 second. The magnet of the stepping switch must, therefore, com- 

 plete the movement of the armature in a minimum of .045 second 

 and the switch must acUance a single step in a minimum of .025 

 second. In addition, the slow-release relay must remain opcratetl 

 for a maximum of .100 second ; for if it releases during the break-pulse 

 period, the circuit to the stepping switch will be opened. These 

 time values assume that the pulse relay accurately reproduces the 

 dial pulses and it is e\ident that to accomplish this, its time of opera- 

 tion and release must be independent of the battery potential, be- 

 tween the \oltage limits prescribed for the battery, and must also 

 be independent of the differences l^elween the electrical constants 

 of different lengths of substation loops. These are difficult require- 

 ments and a punched-type general utility relay, shown in Fig. 13, 

 was used for the inirpose as it af)peared to be the most suitable avail- 



