M.  Muneeswaran, P.  Jenopaul, R.  Sundaraguru, G.  Sridhar, J.  Deny, M.  Sreedevi, 
    Real Implementation of Arm 9 Processor Based Digital Private Branch Exchange,
    Journal of Mobile Communication,
    Volume 6,Issue 3,
    2012,
    Pages 38-42,
    ISSN 1990-794x,
    jmcomm.2012.38.42,
    (https://makhillpublications.co/view-article.php?doi=jmcomm.2012.38.42)
    Abstract: PBX (Private Branch Exchange) is introduced for providing internal calls without cost. In the beginning, analog PBX is developed for internal communication. It has low voice and cross talk errors. Those errors were eliminated by developing digital PBX using Pentium-I processor CPU board. It shows results in much product cost, larger in size and demand for Pentium processors (Obsolete model) also increased rapidly in these days. In this study, implement a digital PBX system CPU using 32-bit ARM 9 processor (S3C2440) which is a compact and cost effective design when compared existing system. A PBX is mainly used in companies, hotel and private complexes.
    Keywords: S3C2440A;digital cross point switch (MT8980);DTMF receiver (MT8870);CPU board;India