1406 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1953 



mounting on a vertical panel interchangeably with existing polar types. 

 The terminals, which may be up to eight in number, are also brought out 

 at the rear for test purposes. 



HIGH-FREQUENCY SWITCHING 



The small size, sjnnmetry, and simplicity of the vertical switch struc- 

 ture has been found to be particularly well adapted for incorporation 

 into coaxial structures for high-frequency switching and it is being used 

 for a variety of apphcations of this kind. 



USES 



Small scale production of the relays has been started for a few special 

 uses. Designs for larger scale uses are still in a preliminary stage. In gen- 

 eral, it is expected that the relay will be well adapted for applications 

 where a transfer contact in combination with low inductance, high speed, 

 high sensitivity, low contact resistance, freedom from chatter, good high 

 frequency switching characteristics, stability, long life, or any combina- 

 tion of these, is required. 



Appendix 



magnet strength versus sensitivity 



A simplified representation of the magnetic system of a relay of this 

 general type is shown in Fig. 11. Here the armature is shown working 

 between two magnetic poles A^ and aS^, each of which has an area A . The 

 armature position is indicated as a deviation ^ toward N from the mid 

 position, and is hmited in its motion by stops at / = zb^i from moving 

 through the full magnetic gap range, defined by the positions / = d=/2 . 



M, and Mn are MMF's in ampere turns, introduced by the magnets 

 on either side, with positive values as indicated by the arrows. Similarly, 

 Me represents the MMF introduced by the operating coil. These values 

 are not those of the magnets and coil in the actual relay. Instead they 

 are assumed to be "Thevenin" equivalent open circuit values of MMF 

 looking away from the working gaps on either side. The gaps are assumed 

 to have the simple geometric dimensions of length li — t and li + /, and 

 area A. The reluctances looking away from the working gaps are as- 

 sumed to be represented by the fixed gaps of area A and length I2 — l\ on 

 either side. 



