Tutorial, digital private branch exchanges (PBXs) 
edited by Edwin R. Coover 
 - Washington, D.C.  IEEE computer Society  1989 
 - ix, 384 p. : ill. ; 28 cm. 
<br/><br/>BIbliography : p. 377-381 
<br/><br/><label>ISBN: </label>0818608293 
<br/><br/><label>LCCN: </label>88-82227 
<br/><br/><label>Subjects--Topical Terms: </label><br/>Telephone--Private branch exchanges<br/>Telephone switching systems, Electronic<br/>Private branch exchange telephone equipment industry<br/>Digital electronics