NEAV GENER.\L PURPOSE RELAY 1033 



By using dilTerent coinhiiuit ions of stal ionai'v and 1 win w iic assemblies 

 with each card variety, a large number of different contact combinations 

 may be obtained. While most of these needed for telephone switching 

 S3^stems use either no sequences at all or a single stage of sequence, a 

 ivw combinations are provided with "preliminary" contacts. These com- 

 binations include two stages of sequence, in which some contacts operate 

 at each of three different points in the armature travel. The preliminary 

 contacts operate earliest in the travel. These are followed by the early 

 contacts of sequence transfers and finally by the late contacts, including 

 ordinary makes and breaks. 



To be sure the desired sequences will be maintained during the life 

 of the relays, it is necessary to provide margins in the form of armature 

 travel allowances at each stage. Combinations with sequences will there- 

 fore require total armature travels which are longer than those with no 

 sequences, and two stages of sequence will require more travel than a 

 single stage. According^, the AF relay is provided with a choice of three 

 armature travels to correspond with the number of sequences needed. 

 At the card, these travels are 0.02G inch (short) for no sequences, 0.044 

 inch (intermediate) for one stage and O.OGO inch (long) for two stages. 



Thus, combinations including ordinary makes, breaks and non-se- 

 quence transfers use short traA'el. Where sequence transfers are also 

 needed, intermediate travel is used and the early contacts of the se- 

 fiuence transfers operate first. Long travel is used only where prelim- 

 inary contacts followed by seciuence transfers are needed. 



5. ARMATURE SYSTEM AND MAGNETIC CIRCUIT 



The armature system and the associated magnetic circuits constitute 

 the basic motor element of an electromagnetic relay. The size of the 

 motor element is determined, in part, by the work it must do and here 

 a basic factor is the contact force. On the basis of analytical as well as 

 experimental studies, it was decided to use a contact force of about six 

 grams per single contact, i.e., about twelve grams for the combined force 

 of the twin contacts. Other important factors which react on the design 

 of the magnet are the speed reciuii-ed, winding space, heating,^ sensitiv- 

 ity, etc. The detailed analysis of the magnetic S3^stem and the asso- 

 ciated measurements will be coxcred in separate papers. 



The magnetic structure chosen is shown in Fig. 8. The armature is a 

 flat member of I' shape whicli piox'ides desiiably large jiole face areas. 



•5 R. L. Pock, Jr., "Internal Temperatures of l{ela\' Wiiiding.s", Hell Sijtitcin 

 Tech. J., Jan., 1951, p. 141. 



