Das, P N <br/><br/>
Introduction to Manual Telephony 

 - Calcutta  Modern Book Agency Privete Ltd  1978 
 - p.149 
<br/><br/><label>Subjects--Topical Terms: </label> Inter Communication Systems  Telephone Relays  Automatic Working 
<br/><br/><label>Dewey Class. No.: </label>621.385 D229I