514 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1953 



Organization of the Engineering Profession. D. A. Quarles^ Elec. Engg., 

 71, pp. 963, 964, Nov., 1952. 



Since the organization of the American Society of Civil Engineers 100 years 

 ago, professional engineering has assumed a major role in American life. The 

 goal now to be attained is the closer organization of the entire engineering pro- 

 fession. 



We begin a New Institute Year. D. A. Quarles^. Elec. Eng., 71, pp. 

 867-868, Oct., 1952. 



In an address before the recent Pacific General Meeting in Phoenix, Mr. 

 Quarles, President of the Institute, evaluates the evolution in A.I.E.E. organiza- 

 tion and poHcy as the Institute enters a new administrative year. 



Mean Free Paths of Electrons in Evaporated Metal Films. F. W. 

 Reynolds^ and G. R. Stilwell^ Letter to the Editor. Phys. Rev., 88, 

 pp. 418-419, Oct. 15, 1952. 



Single-Sidehand System for Overseas Telephony. N. F. Schlaak^ Elec- 

 tronics, 25, pp. 146-149, Nov., 1952. 



Single-sideband transmitter furnishes four voice channels for overseas tele- 

 phone service. Pushbutton tuning permits rapid frequency shifts and load- 

 control circuit minimizes interchannel crosstalk and out-of-band radiation. 

 Copper-oxide and germanium varistors replace modulator tubes. 



Automatic Toll Switching Systems. F. F. Shipley^ A.I.E.E., Trans., 

 Commun. and Electronics Sect., 2, pp. 261-269, pp. 889-897, Oct., 1952. 

 (Monograph 2015). 



The new system was designed to implement the nation-wide switching plan 

 which integrates the telephone switching network of the entire nation into a 

 single unit. Requiring a high order of mechanical intelUgence, this system is one 

 of the most comprehensive ever devised. 



Properties of M-1740 p-n Junction Photocells. J. N. Shive^ I.R.E., 

 Proc, 40, pp. 1410-1413, Nov., 1952. 



The p-n junction photocell has a sensitivity of 30 ma per lumen for light of 

 2,400 degrees K color temperature, corresponding to a quantum yield approxi- 

 mately unity in the spectral range from visible to the long wave cutoff at 1.8 

 microns. Dark currents of a few microamperes are observed at room temperature, 

 with a temperature coefficient of about -|-10 per cent per degree C. Both dark 

 and light currents exhibit saturation in the range from 1 to 90 volts applied. The 

 frequency response is flat into the 100-kc region. Short-circuit noise currents are 

 observed around 20 Ai^a in a 1-cps band at 1,000 cps. The photocell element is 

 encapsulated in a plastic housing ^i X Me X % inch in dimensions. 



1 Bell Telephone Laboratories. 

 ' Sandia Corporation. 



