PREFACE 



Laboratories for wirewound resistors ; Westinghouse Brake and Signal 

 Co., for copper-oxide rectifiers and diodes; A. H. Hunt (Capacitors) 

 Ltd., for metallized paper capacitors; Ferranti Ltd., and the British 

 Thomson-Houston Co. Ltd., for junction diodes; Standard Telephones 

 and Cables Ltd., for a selenium diode; and MuUard Ltd., for 'Ferrox- 

 cube' cores and bobbins, and for permission to reproduce parts of 

 their 'Ferroxcube' handbook. 



Part III is devoted to transducers in the broad sense; that is, it 

 includes chapters on electrodes and on indicators. This part has been 

 written largely by colleagues whom I regard as experts in their several 

 fields, and for whose wilHng co-operation I must record my appreciation 

 and thanks. 



In Part IV, I have tried to draw together all that has gone before, 

 to discuss complete pieces of apparatus, indicating how they are 

 assembled from 'functional units', and how to design, use, and maintain 

 them. 



With the needs of the biologist new to electronics in mind, my aim 

 has been to provide in one volume both a textbook which begins with 

 first principles and a work of reference. Naturally, no book alone can 

 replace a proper course of technical instruction with appropriate 

 practical work, but if the reader will 'lash-up' for himself, and experi- 

 ment with, some of the circuits given as he reads about them ; and if 

 he can find time to follow the technical magazines, paying as much 

 attention to the advertisements as to the editorial matter (one learns 

 much about components in this way), then it is my hope that he will 

 be able to design, and construct for himself, electronic apparatus 

 which will serve him well. 



Finally, I wish to thank Professor Sir Bryan Matthews for his support 

 and encouragement ; my colleagues in this Laboratory for many valuable 

 discussions; Drs. R. H. Adrian and G. S. Brindley, for criticizing and 

 checking the text; Miss Ahson Howlett, who took the photographs; 

 and my Wife, who performed many hundreds of calculations involved 

 in plotting out the graphs. 



P. E. K. D. 

 Physiological Laboratory ^ 

 Cambridge, 1958 



xu 



