Narrowcast

A narrowcast is the transmission of data to a specific list of recipients. Cable television is an example of narrowcasting since the cable TV signals are sent only to homes that have subscribed to the cable service. In contrast, terrestrial TV uses a broadcast model in which the signals are transmitted everywhere and anyone with an antenna can receive them.

The Internet uses both a broadcast and a narrowcast model. Most Web sites are on a broadcast model since anyone with Internet access can view the sites. However, sites that require one to log-in before viewing content are based more on the narrowcast model. Push technologies which send information to subscribers are another form for narrowcasting. Perhaps the best example of narrowcasting are electronic mailing lists where messages are sent only to individuals who subscribe to the list.

The terms multicast and narrowcast are often used interchangeably, although narrowcast usually refers to the business model whereas multicast refers to the actual technology used to transmit the data.

Scope

Since 1985, cable programmes have been protected by copyright law. Copyright, Designs and Patents Act 1988 defines a cable programme to mean any item included in a cable programme service which exists wholly or mainly in sending visual images, sounds, or other information by means of a telecommunication system, otherwise than by wireless telegraphy, for reception either (a) at two or more places (not necessarily simultaneously) or (b) for presentation to members of the public.

In addition to familiar cable television services, a cable programme service might include a non-interactive online database service. It thus excludes interactive systems like teleshopping or internal business services, individual domestic services, services on single-occupier premises otherwise than by way of business amenity, Intranets, et al.

Commercial application

Narrowcasting is particularly useful as a commercial advertising tool. Pre-recorded television prgrammes are often broadcast to captive audiences in taxi cabs, buses, elevators and queues (such as at branches of the Post Office in the United Kingdom). The theory being that, by identifying particular demographics viewing such programmes, advertisers can better target their markets.