The introduction of Cellular Digital Packet Data technology (CDPD) came about after the build out of the cellular voice systems in the United States. The designers of those systems realized a part of that technology was not being used that could send short burst packets of data without interfering with the voice transmissions. The definition of CDPD would be: “CDPD is a technology intended to provide packet data networking services to mobile hosts. The method used consists of radio channels typically used for Advanced Mobile Phone Systems (AMPS) cellular service.”