By Roger C. Greenhalgh and Marshall R. Childs, IBM Corporation
Over the past several years, many new uses of CATV have been examined by the industry. These have tended to be oriented to private homes due to the nature of the present services being rendered. We argue here that data transmission services for the business community represent a viable opportunity.
As contrasted with new home services, the data transmission needs of businesses are well established. The uses of data transmission are known, the amount can be measured, and the demand is strong and growing.
Several new data transmission services have been introduced recently and others are on the horizon. We refer to the various special data carriers and the advent and extension of satellites and microwave. All of these are long-distance services, both high-speed and low-speed in nature.
CATV systems have at least three distinct advantages for local data distribution. First, the channels are inherently high speed. They will permit computer systems to develop along lines where communication speed is matched to computing speed, which in turn will make new uses of computers possible.
Second, the relatively fixed connection pattern of boxes in a data system is known, thus permitting the shared use of cables and limiting the need for extensive switching hardware at some central site.
Third, the CATV facilities can be shared for TV programming and data transmission channels. Thus, the incremental cost for data is low. Also, the two way retrofit of the cable plant provides the capability of handling future home services.
In this paper we discuss the technical environment of CATV and data systems, and review the relative merits of design approaches for the necessary facilities.