Toyota Celica 2005 Repair Manual page 2269

BE−94
8. OUTLINE OF AVC−LAN
(a) What is AVC−LAN?
AVC−LAN is the abbreviation, which stands for Audio Visual Communication−Local Area Network.
This is an unified standard co−developed by 6 audio manufactures associated with Toyota Motor Cor-
poration.
The Unified standard covers signals, such as audio signal, visual signal, signal for switch indication
and communication signal.
(b) Objectives
Recently the car audio system has been rapidly developed, and functions have been changed drasti-
cally. The conventional system has been switched to the multi−media type such as a navigation sys-
tem. At the same time the level of customers needs to audio system has been upgraded. This lies be-
hind this standardization.
The concrete objectives are explained below.
(1) When products by different manufactures were combined together, there used to be a case that
malfunction occurred such as sound failure. This problem is resolved by standardization of sig-
nals.
(2) Various types of after market products can be add or replace freely.
(3) Because of the above (2), each manufacture has been concentrated on developing products in
their strongest field. That enable manufactures to provide many types of products inexpensively.
(4) Generally, a new product developed by a manufacture could not be used with other manufac-
tures products due to a lack of compatibility. Because of this new standard, users can enjoy com-
patible products provided for them timely.
(c) The above descriptions are the objectives to introduce AVC−LAN. By this standardization, develop-
ment of new products will no longer cause systematic errors, and thus it is very effective for the future.
HINT:
When +B short or GND short is detected in AVC−LAN circuit, communication stops. Accordingly the
S
audio system does not function normally.
When audio system is not equipped with a navigation system, audio head unit is the master unit. (When
S
audio system is equipped with a navigation system, navigation ECU is the master unit.)
The car audio system using AVC−LAN circuit has a diagnosis function.
S
Each product has its own specified numbers called physical address. Numbers are also allotted to
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each function in one product, which are called logical address.
2005 CELICA (RM1131U)
BODY ELECTRICAL − AUDIO SYSTEM
2268