Perkins, W. T. <br/><br/>
Modern Telegraph Systems and Equipment, Covering Voice Frequency, Telex, Subaudio and Varioplex Systems, and all Types of Modern Apparatus Including the Teleprinter, Teletypewriter and Creed Automatic 5-Unit and Morse Equipment 

 - London :   George Newnes,   1946. 
 - 215 p. :   tela ;   18 cm.