ARCING OF CONTACTS IN TELEPHONE SWITCHING CIRCUITS 1241 



approximated by: 



2y 



Fo + ^ • - (7o - t;) 



(6) 



where z = (//c)'''. 



Our measurements were then applied to demonstrate the plausibility 

 of the above description of the local circuitry at the contact. This was 

 done in the foUomng fashion, v was obtained by three methods. (1) 

 Measurements were made of the multiple discharges preceding a steady 

 arc, from records similar to Fig. 4(B), and v was calculated from Equa- 

 tion 3, (2) measurements were made of the maximum current attainable 

 during the multiple discharge period, from records similar to Fig. 5(A), 

 and V was calculated from the expression 



/max = H^O 



(a) 



CONTACTS 



Jr 



•'© 



DISTRIBUTED 



r,l,c 



f 



_r 



f 



MAIN 

 CIRCUIT 



(b) 



Vo^' 



^^ 



U 



TIME 



(c) 



2(10)^2 TIME-^^ 



Fig^ 8 — (a) Representation of local circuitry at contacts, (b) Voltage transi- 

 ent at contacts during one discharge of local circuitry, (c) Current transient at 

 contacts during one discharge of local circuitry. 



