Das, P.N. <br/><br/>
Introduction to manual Telephony 

 - Culcutta  Modern Book Agency   1978 
 - p.152 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Manual Telephone Working<br/>Inter Communication Systems
<br/><br/><label>Dewey Class. No.: </label>621.385 D229I