Abrahams, John R. <br/><br/>
Centrex or PBX  the impact of IP 

 - Boston  Artech House  2003 
 - xv,161p.  23cm. 
<br/><br/><label>ISBN: </label>158053497X 
<br/><br/><label>Subjects--Uniform Titles: </label><br/>Contrex telephone service<br/>Telephone-Private brance exchanges<br/>Internet telephony
<br/><br/><label>Dewey Class. No.: </label>621.385  / A16C