Technical Instructrns :  explanatim of the standard system of duplex and D. C. Simplex telegraphy in use in India / 
Telegraph dept, Govt of India 
 - Calcutta :  Govt. Press,  1915 
 - 9 p. ;  32 cm. 
<br/><br/><label>Dewey Class. No.: </label>621.3823