Audio System: Description

The radio wave bands used in Identifying radio broadcasting are as follows:

Fig 1: Radio Broadcasting Frequency Chart

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

LF: Low Frequency

MF: Medium Frequency

HF: High Frequency

VHF: Very High Frequency

There are great differences in the size of the service areas for AM and FM broadcasts. Sometimes FM stereo broadcasts cannot be received in an area where AM broadcasts can be received very clearly.

Not only does FM stereo broadcasts have the smallest service area, but it also picks up static and other types of interference ("noise") easily.

Besides the problem of static, there are also the problems called "fading", "multi-path" and "fade out". These problems are not caused by electrical noise but by the nature of the radio waves themselves.

1. Fading:

   Besides electrical interference, AM broadcasts are also susceptible to other types of interference, especially at night. This is because AM radio waves bounce off the ionosphere at night. These radio waves then interfere with the signals from the transmitter which reach the vehicle's antenna directly. This type of interference is called "fading".

   Fig 3: Identifying Fading

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Multi-path:

   One type of interference caused by bounce of radio waves against obstructions is called "multi-path". Multi-path occurs when a signal from the broadcast transmitter antenna bounces off buildings and mountains and interferes with the signal that is received directly.

   Fig 4: Identifying Multi-Path

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3. Fade Out:

   Because FM radio waves are of higher frequencies than AM radio waves, they bounce off buildings, mountains, and other obstructions. For this reason, FM signals often seem to gradually disappear or fade out as the vehicle goes behind buildings or other obstructions. This is called "fade out".

   Fig 5: Identifying Fade Out

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Compact disc players use a laser beam pick-up to read the digital signals recorded on the CD and reproduce analog signals of the music, etc.

1. MAINTENANCE 

1. Raise the cassette door with your finger. Next, using a pencil or similar object, push in the guide.
2. Using a cleaning pen or cotton applicator soaked in cleaner, clean the head surface, pinch rollers and capstans.
   Fig 6: Identifying Tape Player Head, Capstan & Pinch Roller

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. MAINTENANCE 

If a disc becomes dirty, clean the disc by wiping the surface from the center to outside in the radial directions with a soft cloth.

Fig 7: Cleaning CD Player Disc

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. What is AVC-LAN?

   AVC-LAN is an abbreviation, which stands for Audio Visual Communication-Local Area Network. This is a unified standard co-developed by 6 audio manufactures associated with Toyota Motor Corporation.

   The unified standard covers signals, such as audio signals, visual signals, signals for switch indications and communication signals.

2. Objectives

   Recently the car audio system has been rapidly developed and functions have been changed drastically. The conventional system has been switched to the multi-media type such as a navigation system. At the same time, the level that customers needs to audio systems has been upgraded. These cause lie this standardization.

   The concrete objectives are explained below.

   1. When products made by different manufactures were combined together, there used to be a case that a malfunction occurred such as sound did not come out. This problem has been resolved by the standardization of signals.
   2. Various types of aftermarket products have been able to added or replaced freely.
   3. Because of the above (2), each manufacture has become able to concentrate on developing products in their strongest field. This has enabled many types of products to be provided inexpensively.
   4. Conventionally, a new product developed by a manufacture could not be used due to a lack of compatibility with other manufactures products. Because of this new standard, users can enjoy compatible products provided for them timely.
3. The above descriptions are the objectives to introduce the AVC-LAN. By this standardization, development of new products will no longer cause systematic errors. Thus, this is very effective standard for a product in the future.
   NOTE:

   • When +B short or GND short is detected in the AVC-LAN circuit, communication stops. Accordingly the audio system does not function normally.
   • When an audio system is not equipped with a navigation system, audio head unit is the master unit. (When an audio system is equipped with a navigation system, the radio receiver is the master unit.)
   • A car audio system using the AVC-LAN circuit has a diagnosis function.
   • Each product has its own specified numbers called physical address. Numbers are also allotted to each function in one product, which are called logical address.