REFERENCES 



part from the upper cathode ray tube Y deflector plate. A small loud- 

 speaker is included in the capacitor discharge path. A rather lugubrious 

 musical note is emitted at a pitch which depends on the level of the cathode 

 ray tube trace. With practice it is possible to make a good estimate of the 

 latter by listening to the sound. 



To CRT 



y deflector 

 plate 



20M 



HT* 



Sensitivity 

 control 



\] 3ft loudspeaker 



Figure 39.25 



Penwriter amplifiers 



Penwriters are usually bought, and the manufacturers commonly supply 

 a main amplifier specially designed to go with them. The transient and 

 frequency response of penwriters depends upon the damping placed across 

 them by the output resistance of the amplifier ; therefore the two have to be 

 designed together. Readers who are interested in home-made types may 

 care to consult Grey Walter and Brooks^' (who describe an entire E.E.G. 

 apparatus) and Tanner and Harrington^^. 



REFERENCES 



^ Dawson, G. D. Electroenceph. Clin. Neuwphysiol. 6 (1954) 65 

 ^ Dickinson, C. J. Electrophysiological Technique. Electronic Engineering 

 ^ Yarwood, J. and Le Croisette, D. H. Electron. Engng. 26 (1954) 14 

 * Bishop, P. O. and Harris, E. J. Rev. sci. Instrum. 21 (1950) 366 

 5 AsHER, H. Electron. Engng. 23 (1951) 170 

 « Matthews, B. H. C. /. Physiol. 122 (1953) 2P 

 ' Nielsen, S. O. and Rosenberg, T. /. sci. Instrum. 31 (1954) 401 

 ^ Waveforms. Radiation Laboratory series, McGraw-Hill 



^ Palevsky, H., Swank, R. K. and Grenchik, R. Rev. sci. Instrum. 18 (1947) 298 

 1" Thomas, D. G. A. and Finch, H. W. Electron. Engng. 22 (1950) 395 

 " Lampitt, R. a. Electron. Engng. 18 (1946) 347 

 12 Preston, J. S. /. sci. Instrum. 23 (1946) 113 

 " Hill, A. V. J. sci. Instrum. 25 (1948) 225 



" Frankenhaeuser, B. and Macdonald, D. K. C. J. sci. Instrum. 26 (1949) 145 

 1^ Dickinson, C. J. Electrophysiological Technique. Electronic Engineering 

 i« Draper, M. H. and Weidmann, S. /. Physiol. 1 15 (1951) 74 

 " Grey Walter, W. and Brooks, A. A. Electron. Engng. 19 (1947) 221 

 1^ Tanner, J. A. and Harrington, B. G. V. /. sci. Instrum. 28 (1951) 33 



637 



