88 BELL SYSTEM TECHNICAL JOURNAL 



same length and are provided with soldering eyelets for individual or 

 non-multiple wiring. 



The multi-contact relay finds its chief use in the common connector 

 circuits where a large number of leads must be connected simultane- 

 ously to a common circuit. 



U and Y Type Relays 



New and improved general purpose small relays which have been 

 coded the "U" and " Y" type are used in this system. Figure 6 shows 

 a typical "U" type relay. Although somewhat similar to the E and 

 R type relays which have been in a common use in the telephone 

 systems for many years, it differs from them principally in that it 

 has a heavier and more efficient magnetic structure which permits 

 the use of a greater number of contact springs. These relays permit 

 the use of spring assemblies up to a maximum of 24 springs in various 

 combinations of springs, including transfer contacts, simple make- 

 and-break contacts. The relays are constructed of relatively simple 

 parts, most of which are blanked and formed in the desired shapes in 

 the same manner as the earlier E and R type relays. The cores are 

 made from round stock and are welded to the mounting bracket of 

 the relay. The structures of all of these relays are similar and differ 

 principally in their spring assemblies and windings. 



In order to insure more reliable contact closures, the relays are 

 equipped with twin contacts. Various types of contact metal and 

 sizes of contacts are provided, depending upon the characteristics of 

 the circuit controlled by the contacts. 



Improved methods of clamping the springs in their assemblies, 

 together with the design of the springs, provide stability and minimize 

 manufacturing and maintenance adjusting effort. 



Contacts practically free from chatter on both the operation and 

 release of the relay have been obtained by the use of relatively heavy 

 stationary springs, short thin movable springs, and a pivoted arrange- 

 ment of the armature suspension. By reference to Fig. 6 it will be 

 seen that the rear ends of the armature are pivoted by two pins which 

 project through holes in the hinge bracket mounted on the rear spring 

 assembly. In the earlier flat type relays of the E and R type, the 

 armature was suspended at the rear by means of a reed type armature 

 hinge. 



The Y type relays make use of the same manufacturing tools and 

 processes as the U type. Copper or aluminum sleeves are provided 

 over the cores beneath the windings to secure the slow-release char- 

 acteristics required on these relays. The relay armature is embossed 



