"In 1983, IBM developed a private packet radio data network called DCS (Data
Communication System) for the use of its field engineers. This was used for call
dispatch and call reporting and some other data applications. The terminal
device consisted of a hand held data terminal about the size and shape of a
house brick, by which name it was consequently known. The radio infrastructure
was provided by Motorola and operated at 4.8 Kbps on a carrier frequency of 800
MHz. The network covered the major cities of the United States but the FCC
licence did not allow the service to be sold to other users. At the same time,
Motorola was building a network using the same technology for public access.
In 1990, the IBM and Motorola networks were joined to form a public access
network known as ARDIS (Advanced Radio Data Information System). The
original implementation of ARDIS used a protocol known as MDC4800, but a new
protocol called RD-LAP is being introduced alongside with the advantage of
operating at 19.2 Kbps."
SG24-4465-01 page 14