448 



THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1952 



finger to engage and move the wheel in either direction to one of ten 

 detented positions. All of the wheels may be returned to their normal 

 "zero" position simultaneously by depressing the release button on the 

 front right corner of the housing. To place a call the subscriber positions 

 each of the wheels so that the desired number may be read across the 

 wheels on the line of indentations immediately above the lower edge of 

 the enclosing frame. The first three wheels are set to the code of the 

 called office and the next five to the called line directory nimiber with 

 the last of these being used for the party letter, if required. A number 

 is preset in this manner before the handset is removed from its cradle 

 across the back of the housing. With this method of operation the num- 

 ber may be rapidly and completely transmitted to the central office 

 when its receiving circuit has been connected to the line. 



CONTACT 



leads: 



FRONT -- 

 BACK 



UPPER POLE 

 PIECE -^^^ 



contacts: 



ARMATURE ' 



FRONT 

 BACK 



ARMATURE- 



LOWER POLE 

 PIECE 



COIL- 



TUBULAR 

 STEM " 



WAX 

 FILLING 



\_ FELT 



WASHER 



WELD-'- 



■--MEDIUM 

 OCTAL BASE 



Fig. 4 — Mercury contact relay. 



