AUTOMATIC TESTING IN TELEPHONE MANUFACTURE 



1147 



gas tube to fire and the relay to operate. The circuit is designed to handle 

 a wide range of pulse amplitudes. The VR tube Hmits negative pulses to 

 90 volts to protect the 6AK5. The varistor dissipates positive pulses and 

 prevents any false acceptance that might be caused by damped oscilla- 

 tions following a positive pulse. The 6AK5 furnishes the needed sensi- 

 tivity for small pulses. 

 Occasionally a winding will have a value of resistance just equal to 



.5MEG 



I— vw 



+ 130 



PICKUP COIL 

 30,000 TURNS 

 ON PERMALLOY 



50 K 



Mitt 



QUENCH 



CIRCUIT 

 FOR NEXT 

 TEST 



UNLOCK 



AAA/ M 55V. AC l^c.T. GROUNDED 



/ONE SIDE OF IIOV. AC\ 



(A) 



^; 



SENSITROL 



RESET <|_r 

 SOLENOID -• P 



50MF-r 



SLOW 

 RELEASE 

 3 SEC. 



20 K 



1 



(B) 



Fig. 7 — Circuits used in relay coil test set. (a), direction of winding, simpli- 

 fied schematic; (b) anti-stall, simplified schematic. 



