598 



BELL SYSTEM TECHNICAL JOURNAL 



ode over the previous designs. To make this tube rugged, both electrodes 

 were supported from large diameter kovar-to-glass seals. During assembly 

 the cathode end of the tube was open so that a tool could be inserted to 

 hold the anode concentric with respect to the cathode, while its supporting 

 member was sealed to the glass. A cup was then brazed in to cover the cath- 

 ode opening. 



Fig. 23 — Western Electric 1B31 spark gap tube. 



Several hundred models of this tube were made in the laboratory and 

 performed satisfactorily in the circuit. Due to circuit design changes, 

 however, these tubes did not go into large scale manufacture. 



W.E. 1B42 



The 1B42 fixed gap tube departs considerably in design from the 1B22 

 and 1B29 in that mercur}- instead of aluminum was used as cathode. Its 



