REMOTE CONTROLLED LINE CONCENTRATOR 



263 



EMITTER 



COLLECTOR 



EMITTER 



n-p-n 



COLLECTOR 



BASE 



fa) 



POINT CONTACT 

 TRANSISTOR 



Ic 



BASE 



(b) 



CONJUGATE PAIR 



ALLOY JUNCTION 



TRANSISTORS 



C _ 



0C> 1 



Fig. 9 — Point contact versus hooked conjugate pair. 



pulse is fed into the emitter (of the pair) causing the emitter diode to 

 conduct. The base potential is increased thus increasing the current 

 flowing in the collector circuit. When the input pulse is turned off the 

 base is left at about —2 volts thus maintaining the emitter diode con- 

 ( lucting and continuing the increased current flow in the collector circuit. 

 The diode in the collector circuit prevents the collector from going 

 positive and thereby limits the current in the collector circuit. To reset, 

 a positive pulse is fed into the base through a pulse gate. The driving of 

 tlie base positive returns the transistor pair to the off condition. 



c. Transistor Pulse Amplifier 



This circuit (Fig. 11) is formed by making a bi-stable self resetting 

 circuit. It is used to produce a pulse of fixed duration in response to a 



TRANSISTORS 



p-n-p 



SET 



RESET 



I-5V 



-I6V 



F/F 



Fig. 10 — Transistor bi-stable circuit. 



