Navigation System: Description and Operation
DESCRIPTION1. OUTLINE OF AVC-LAN
a. What is AVC-LAN?
AVC-LAN is the abbreviation for Audio Visual Communication-Local Area Network. This is a unified standard co-developed by 6 audio manufacturers associated with Toyota Motor Corporation.
The unified standard includes signals, such as audio, visual and signals for switch indication and communication.
b. Objectives
Recently developments in car audio systems have been rapid 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 customers want to upgrade their audio systems. This is the factor that lies behind this standardization.
The concrete objectives are explained below.
1. When products by different manufacturers were combined together, malfunctions such as sound failure occurred. This problem can be solved by standardization of signals.
2. Various types of after market products are available.
3. Because of the above (2), each manufacturer has been able to concentrate on developing products in their strongest field. This has enabled development of inexpensive products.
4. In general, a new product developed by a particular manufacturer could not be used due to a lack of compatibility with other manufactures products. By developing this new standard, users can enjoy a range of compatible products from different manufacturers.
c. The above stated are the reasons for the introduction of AVC-LAN. Under this standardization, development of new products no longer causes systematic errors.
HINT:
- When +B short or GND short is detected in AVC-LAN circuit, communication stops, and the audio system does not function normally.
- When the audio system is not equipped with a navigation system, the audio head unit is the master unit. When audio system is equipped with a navigation system, the radio receiver is the master unit.
- The master unit is equipped with a resistor (60 to 80 Ohms) for communication.
- The car audio system using AVC-LAN circuit has a diagnosis function.
- Each product has its own specified number called a physical address (three-digit number). Numbers are also allotted to each function within a product, which are called logical addresses (two-digit number).
2. COMMUNICATION SYSTEM
a. This system performs communication between components through the Main AVC-LAN and Sub AVC-LAN.
b. In this AVC-LAN, the multi-display assy becomes the master of the communication, and the radio receiver assy has a resistance (60 to 80 Ohms) necessary for transmitting the communication.
The television camera ECU and the multi-display assy is connect between the navigation ECU and the radio receiver assy. LEXUS navigation system is structured so that communication is impossible without the navigation ECU, the television camera ECU, the multi-display assy or the radio receiver assy.
HINT: Refer to "REAR SEAT ENTERTAINMENT SYSTEM" for the Sub AVC-LAN circuit.
c. The radio receiver assy is equipped with a resistor (60 to 80 Ohms) for communication.