Hitachi AXM75DAB Instruction Manual page 21

Guide to digital radio
Your unit enables you to receive and listen to DAB radio programmes. Digital Audio Broadcast
(DAB) uses digital signals rather than traditional analogue signals enabling near CD-quality
audio with virtually interference-free reception. DAB also enables broadcasters to transmit
additional data along with the audio including other audio channels, text and in the future,
perhaps computer data and images.
Digital radio is broadcast as groups of data called ensembles or multiplexes. Each multiplex
can contain a number of stations (services) and each station contains a primary service and
can contain secondary services as illustrated in the following diagram.
Each multiplex is transmitted in a set frequency range and received by your unit for decoding.
Your unit enables you to receive multiplexes broadcast in frequency band lll (174-240 MHz)
and store the services in each multiplex for you to access. The number of multiplexes you
receive will vary depending on your location. Band lll is divided into 41 channels identified as
5A to 13F. Each channel can contain one multiplex. Channels allocated to the UK are in the
range 11B to 12D.
Multiplexes and stations have labels (names) which are used to identify them. Instead of needing
to know a particular frequency to listen to your favourite broadcast you can simply select the
station name. Secondary services and additional data such as text containing programme or
multiplex information are also easily accessed using your unit.
BBC National DAB
(Primary) BBC Radio 4
(Secondary) Parliament
AMPLIFIER AND TUNER
DAB SIGNAL
1
1
2
1
2
21
MULTIPLEX
Primary SERVICES
3+
SECONDARY SERVICES
4+
3