1208 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1952 



be for short, intermediate or long periods and inv^olves the retention of 

 information for subsequent use; operations involving addition, sub- 

 traction, multiplication and division; translation of information from 

 one form or code to another; gating, involving the routing of signals 

 according to a predetermined pattern or set of conditions; regeneration 

 of signals in amplitude and wave form; delay, which may be thought 

 of as a form of storage; and timing. Some of these functions are simple; 

 others result from fairly complex structures of simpler functions. 



Present trends in electronic switching systems are toward compli- 

 cated automata as exemplified by digital computers.^ The reliability, 

 power consumption and physical size of the electron devices employed 

 largely determines the degree of realizability of such systems. It is 

 believed that the transistor will find a significant application in this 

 field. 



The transistor can reduce power consumption by the elimination of 

 heater or filament power. In addition, particularly in broadband ap- 

 plications as in high speed pulse systems, the "B" power may be reduced 

 by the order of one or two decades if not more. Transistor circuits with 

 0.02 /iS rise time have been made to operate Avith an input power of 20 

 milliwatts which compares with approximately 2.5 watts (1-watt heater, 

 1.5-watt plate) for an equivalent tube circuit. Transistors have operated 

 with less than one microwatt input power.- 



Such power reductions result from the low operating voltages, low 

 internal resistances and low capacitances of transistors. Low internal 

 impedances greatly reduce the importance of stray wiring capacitances 

 thereby making mechanical design much simpler and often eliminating 

 the need for isolating or buffer amplifiers. 



The transistor can contribute definite reduction in size directly. Fig. 1 

 shows a "bead" transistor which has a volume of approximatelv 1/1000 

 of a cubic inch and a weight of 5/1000 ounce. Indirectly the transistor 

 can contribute to size reduction through the use of smaller, lower voltage, 

 lower dissipation components. The reduction of power supply require- 

 ments in terms of size, regulation and capacity is also quite appreciable. 



Transistors have been subjected to shocks in excess of 20,000 G with- 

 out change in characteristics. Vibration tests have shown no resonances 

 in the transistor shown in Fig. 1 to several thousand cycles. Harmonic 

 accelerations of 100 G at 1000 cycles have produced no detectable cur- 

 rent modulation. 



' L. N. Ridenour, "High Speed Digital Computers", J . Appl. Ph7js., 21, pp. 

 263-270, April, 1950. 



^ R. L. Wallace, Jr. and W. J. Pietenpol, "Some Circuit Properties and Ap- 

 plications of n-p-n Transistors", Bell System Tech. J., 30, pp. 530-563, Jul}', 1951. 



