BALANCED POLAR MERCURY CONTACT RELAY 



1403 



voltages to safe values. A small resistance in series with the condenser 

 to limit the closure current is usually necessary. A considerable amount 

 of very satisfactory experience has been had with inductive loads of 0.5 

 ampere at 50 volts, with 0.5 mf in series with 10 ohms across the con- 

 tacts. 



The contact closure shows no chatter for time intervals of 0.1 micro- 

 second or more. 



LIFE 



Tests of relays with protected contacts indicate that the only change 

 is a sensitivity change due to wear. Under conditions producing fairly 

 high velocity of contact impact this change is of the order of 5 ampere 

 turns increase in differential ampere turns for a billion operations, the 

 change being roughly proportional to the logarithm of the number of 

 operations. 



HORIZONTAL TYPE RELAY 



Most of the apparatus in the telephone plant is mounted on vertical 

 panels. The substantially vertical mounting requirement for the relay 

 shown in Fig. 1 tends therefore to be uneconomical from the space stand- 

 point. Fig. 9 shows a modification of the glass enclosed switch which 

 avoids this limitation by being designed to operate with its axis hori- 

 zontal. 



The switch modification consists in adding to the switch a special 



20 



30 40 50 60 70 80 90 100 110 

 OPERATE AMPERE-TURNS 



Pig 8 _ Release time versus operate ampere turn adjustment. 



