National Extension College. <br/><br/>
Telephone switching systems III : section A : numbering and trunking schemes  [Books]. 
National Extension College. 
 - Cambridge  National Extension College  1982 
<br/><br/><label>ISBN: </label>0860825329  0.00 
<br/><br/><label>Subjects--Personal Names: </label><br/>Telephone switching systems, Electronic.
<br/><br/><label>Dewey Class. No.: </label>TK/6397  / NUM