Langley, Graham. <br/><br/>
Telecommunications primer /  [Book]. 
Graham Langley.  
 - 3rd ed. 
 - London :   Pitman,   1990. 
 - vi, 182p. :  ill. ;  25 cm. 
<br/><br/> Includes index. 
<br/><br/><label>ISBN: </label>0273031872 (pbk) 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Telecommunication systems.