254 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1956 



Table I— Transistor Characteristics 



considerable progress has been made in improving transistors of thi.s 

 type. Table I summarizes the characteristics of these transistors. 



For directing and analyzing the pulses, the control employs semicon- 

 ductor diode gate circuits." The semiconductor diodes used in these 

 circuits are of the silicon alloy junction type,^^ Except for a few diode.s 

 operating in the gas tube circuits most diodes have a breakdown voltage 

 requirement of 27v, a minimum forward current of 15 ma at 2v and a 

 maximum reverse current at 22v of 2 X 10^^ amp. 



4. new techniques employed 



The concentrator represents the first field application in Bell System 

 telephone switching systems which departs from current practices and 

 techniques. These include: 



Fig. 2 — Transistor packages, (a) Diode unit, (b) Transistor counter, (c) 

 Transistor amplifiers and bi-stable circuits, (d) Five trunk unit. 



