In car entertainment ® include Dolby filters to reduce hiss and other

9.7 In car entertainment ® include Dolby filters to reduce hiss and other

(ICE) security and tape selections such as chrome or metal. A digi-

tal display of course, will provide a visual output

communications

of operating condition. This is also linked into the vehicle lighting to prevent glare at night. Track

9.7.1 ICE

selection and programming for one or several compact discs is possible. Figure 9.28 shows a

Controls on most sets will include volume, treble, modern ICE system display and control panel bass, balance and fade. Cassette tape options will

together with a top quality speaker (woofer). Many ICE systems are coded to deter theft. The code is activated if the main supply is dis- connected and will not allow the set to work until the correct code has been re-entered. Some sys- tems now include a plug in electronic ‘key card’, which makes the set worthless when removed.

Good ICE systems include at least six speak- ers, two larger speakers in the rear parcel shelf to produce good low frequency reproduction, two front door speakers for mid range and two front door tweeters for high frequency notes. Speakers are a very important part of a sound system.

Figure 9.26 Windscreen zones

No matter how good the receiver or CD player is,

Figure 9.27 Wiper motor tests

Electrical systems 217

the sound quality will be reduced if inferior speak- ● Traffic information broadcasts can be identi- ers are used. Equally if the speakers are of a

fied and a setting made so that whatever you lower power output rating than the set, distortion

are listening to at the time can be interrupted. will result at best and damage to the speakers at worst. Speakers fall generally into the following

The radio broadcast data system (RBDS) is an categories:

extension of RDS which has been in use in Europe

since 1984. The system allows the broadcaster to tweeters high frequency reproduction;

transmit text information at the rate of about 1200 mid range middle range frequency reproduc-

bits per second. The information is transmitted on tion (treble);

a 57 kHz suppressed sub-carrier as part of the FM woofers low frequency reproduction (bass);

MPX signal.

sub-woofers very low frequency reproduction. RBDS was developed for the North American The radio data system RDS has become a stand-

market by the National Radio Systems Commit- ard on many radio sets. It is an extra inaudible

tee (NRSC), a joint committee composed of the digital signal which is sent with FM broadcasts

Electronic Industries Association (EIA) and the in a similar way to how teletext is sent with TV

National Association of Broadcasters (NAB). signals. RDS provides information so a receiver

The applications for the transmission of text to can appear to act intelligently. The possibilities

the vehicle are interesting and include: available when RDS is used are as follows.

● song title and artist;

● The station name can be displayed in place of ● traffic, accident and road hazard information; the frequency.

● stock information;

● There can be automatic tuning to the best

● weather.

available signal for the chosen radio station. For example, in the UK a journey from the

In emergency situations, the audio system can be south of England to Scotland would mean

enabled to interrupt the cassette, CD, or normal the radio would have to be retuned up to ten

radio broadcast to alert the user. times. RDS will do this without the driver

Figure 9.29 shows a circuit typical of many even knowing.

ICE systems.

Figure 9.28 ICE display and speaker

218 Advanced automotive fault diagnosis

Door switches

Siren

Bonnet switches

Door locking, window

ultra sonic

System LED

Hazard lights

Control

switch

Ignition immobiliser

IR key sensor

Loop circuit

Ignition

switch

Volumetric transmitter

Cranking signal

Figure 9.29 ICE circuit Figure 9.30 Block diagram of a complex alarm system