
Communications
Broadcast networks
The communications that we have spoken about so far are two-way,
or interactive, each party being able to transmit and receive. Broadcast
networks, such as those operated by the BBC and IB A, are one-way,
meaning that only one party, the broadcaster, is able to transmit.
As explained earlier, the broadcast signals are normally in analogue
form, though some, like the Ceefax and Oracle pages put out by the
BBC and IB A, are digital. These signals modulate the carrier waves,
which are sent by land-line to a transmitting station, from where they
are broadcast through the air. They then complete their journey t