Cellular Digital Packet Data is a technique, which is applicable over cellular network for quick transfer of data. It is applicable in providing a quick transfer of data over cellular networks. It transmits the packets over the cellular network in a reliable manner. Packet networks break a stream of data in to independent blocks of data called the packets. CDPD is wirelesses IP network that overlay on the existing AMPS cellular infrastructure. The CDPD raw channel modulation user rate is 19.2 kbps. It provides high speed, high capacity and cost effective data. It performs the important role in its network. It plays important role in credit card verification and ATM networks. With this technology both voice.