WO2023059214A1

WO2023059214A1 - Modular audio system for public passenger transportation vehicles

Info

Publication number: WO2023059214A1
Application number: PCT/RO2022/050009
Authority: WO
Inventors: Gabriel Eugen DOGARU
Original assignee: Radcom S.A.
Priority date: 2021-10-05
Filing date: 2022-10-05
Publication date: 2023-04-13
Also published as: RO135649A3; RO135649B1; RO135649A0

Abstract

The invention refers to a modular audio system for public passenger transportation vehicles. The system, according to the invention, consists of a connector module (MC), a driver's microphone module (MF), at least one audio amplifier module (A), a radio module (R) and an on-board computer (C), distributed in the vehicle and connected in a chain by a single unshielded UTP cable (1), with a single pair of twisted wires, in which the on-board computer (C) controls, using a dedicated software, the entire system and provides automatic location-dependent audio content, the connector module (MC) connects the on-board computer (C) via a USB interface (2) or an Ethernet interface (3) with the other downstream modules through a UTP cable (1), being positioned at the end of the chain where the onboard computer (C) is, the microphone module (MF) captures the driver's voice and provides announcements to the passengers, the audio amplifier modules (A) feed the loudspeakers and can produce an audio volume adapted to each area in which it operates, and the radio module (R) receives radio broadcasts and distributes them to the amplifier modules (A), based on the instructions received from the on-board computer (C).

Description

MODULAR AUDIO SYSTEM FOR PUBLIC PASSENGER TRANSPORTATION VEHICLES

Description

The invention refers to a modular audio system designed to be used in public transportation vehicles for an optimal distribution of the audio content into these vehicles.

Usually, public transportation vehicles have today capabilities to distribute audio content to passengers. This audio content can be location-dependent automatic announcements (route, current stop, next stop, points of interest), driver's or guide's microphone announcements, musical content or audio advertising. In order to provide this functionality a certain audio unit is used consisting of a multiple channel amplifier that feeds loudspeakers around the vehicle (driver's cabin, passenger's area, external areas near the vehicle's doors) and a connection matrix that allows the assignment of the audio content sources to these amplifying channels. Such an audio unit is presented in figure 1. These audio units can be designed using analogue or digital technology, but they are built using similar principles.

A first disadvantage of this solution is the large number of electrical cables, both type A (for connecting audio signals sources- on board computer, driver's microphone, radio receptor- and the distributed audio system, marked A) and type B (used to feed loudspeakers distributed along the whole length of the vehicle, connected to the audio unit, marked B). The electrical diagram of the type B cables that feed only the loudspeakers in the passengers' area may look like in figure 2 or even more complex in the case of long vehicles. More so, type C bifilar cables are needed to control the functions of the audio system (marked with C). This multitude of cables represent a major problem for both the production of the cable forms and also at their installation, increasing the cost of the solution, considering that automotive quality shielded and fire resistant cables are needed. Another disadvantage of this solution is its lack of flexibility in the design of the audio system, which for small vehicles should deliver low power audio signal, but in the case of very long vehicles, such as trams, the audio signal powers should be higher, because of the high number of loudspeakers in the passenger's lounge. Moreover, the installation of external loudspeakers is required just in the case of some vehicles, implying a separate amplifying channel, as the transmitted audio content to these loudspeakers is different. For this reason, several types of audio units should be provided, with a higher number of amplifying channels with different powers, or a too complex and too large audio unit should be accepted, which is too expensive in the case of small vehicles.

A final disadvantage, even more important, is related to the request to adapt the audio content volume to the vehicle's environment noise level, or to the external noise level, measured with environmental microphones (one microphone for each amplifying channel). Based on the microphone assigned to an amplifying channel, placed in a certain position, the convenient audio signal volume can be established for that particular amplifying channel. In the case of long vehicles, the level of the internal environmental noise is different depending on the areas where the passengers are, but the level of the audio signal generated by each amplifying channel, chosen based on the measurement obtained by the corresponding microphone, is unique and even if providing a medium audio level is chosen, certain situations will appear when in some areas the signal is either too low or too high, both of these scenarios creating passengers' discomfort. Usually, it is chosen the safer solution, that is delivering an unique volume adapted to the noisiest area and in this case the passengers in the quieter areas are disturbed by the excessive level of the audio content. The same problem arises in the case of using external loudspeakers installed close to the doors of the vehicle. The level of the audio signal, provided on the channel assigned for these loudspeakers, will be correlated to the noise level measured by the microphone corresponding to that particular amplifying channel. Depending on the positioning of this microphone, the level of the audio signal will be impossible to be correlated to the existing noise level at each door of the vehicle. _T, WO 2023/059214 . , , , , . i «. ,J «. «._K . , ■ CT/R02022/050009. ,

The tecnmcai prooiem solved by the invention is related to the modularization or an auaio unit for different dimensions passenger vehicles that provides at the same time a low number of electrical cables, audio signal power level depending on the vehicle necessities and the adaptation of the audio signal volume to the environmental noise level for each area in or outside the vehicle.

The distributed audio system, installed on board of a vehicle, according to the invention, solves the aforementioned technical problem, consisting of a Connector module, a vehicle driver Microphone module, at least an audio amplifier module, a FM/AM/DAB module and an on-board computer, distributed in the vehicle and chain connected by one single unshielded cable, with a single pair of twisted cables using a well known technology for interconnecting different audio equipment, where:

• the on board Computer controls the whole system, using a dedicated software, and provides the automated location-dependent audio content, consisting of several modules, from which we mention a graphical console (display) that usually has a touchscreen the driver interacts with and a GSM modem that provides data connections with the back-office equipment;

• the Connector Module is interconnected with the on-board Computer via a USB interface or an Ethernet interface and with the other downstream modules via a UTP cable, placing the Connector Module at the end of the chain near the on-board Computer. It consists of:

° a USB/Ethernet interface component that receives from the on-board Computer signals according to USB or Ethernet standards and provides as an output Time Division Multiplex (TDM) audio signals, that include 8 or 16 digital audio channels, with a sampling frequency of 48 KHz and a maximum resolution of 32 bits, and receives from the on-board Computer configuration commands for the modules that form the audio system, transforming them into I2C standard compliant commands and

° a Master transmitter/receiver that modulates the TDM signal and transmits it downstream to the other modules, that will extract the audio channels intended for them, according to the software configuration assigned to each of them, using the I2C commands received by the Master transmitter/receiver and included by it in the signal downstream transmitted to the other modules, allowing their control.

According to one feature of the invention, the TDM signal is also transmitted to the Master transmitter/ receiver in the opposite way, meaning that the TDM signal coming from the modules, consisting of digital audio signals received from the microphones and other audio sources, is converted in USB or Ethernet signals, that reach the on-board Computer in order to be processed.

According to another feature of the invention, the vehicle driver Microphone module contains 2 microphones that receive the vehicle driver's voice or, if the case, of the vehicle's guide and a Slave transmitter/receiver that provides the upstream and downstream connection with other audio system modules, using external switches that allow creating priorities and that are placed on the board of the vehicle, easy accessible for the driver and an echo cancellation block, echo gathered by the 2 aforementioned microphones, during the handsfree VoIP calls progress, this block being controlled via I2C commands by the module's Slave transmitter/receiver.

According to one feature of this invention, the audio Amplifier modules are distributed in different areas: driver's cabin, external loudspeakers area, in case external loudspeakers are required, and several areas in the passenger's lounge, depending on the length of the vehicle, and they consist of a digital amplifier and a microphone, where the amplifier feeds the proximal area loudspeakers with the audio signal received via the audio system chain and the microphone is meant to gather the environmental noise in the surrounding area, which is then sent via the connections chain to the on-board Computer in order to be processed and measured; based on this measurement the audio signal level is regulated in that particular area corresponding to the module connected loudspeakers, so that the optimal audio level is obtained in each area of the vehicle;

According to another feature of this invention, the audio Amplifier modules, each of them, consist of:

• a Slave transmitter/receiver that is connected upstream and downstream to other audio system modules via a UTP cable and controls using I2C commands a digital audio amplifier; • WO 2023/059214 _amp|jfj_er that receives the TDM audio signal from the SPCT/R 2022/050009_ejver and receives from the on-board Computer, via the Slave transmitter/receiver, the command specifying the audio channel that will be amplified and provided to the loudspeakers and the command that sets up the audio signal level delivered to the loudspeakers.

According to another feature of the invention, the audio signal total power delivered to the whole vehicle is achieved by installing the proper number of these modules.

According to another feature of this invention, the FM/AM/DAB radio module consists of a FM/AM/DAB receptor that receives FM, AM and DAB signals via separate antennas and a Slave transmitter/receptor that is used to connect upstream and downstream to other audio system modules via an UTP cable and that allows the distribution of the received radio signals to any of the audio Amplifier modules.

The advantages of using the invention are:

• simple design

• flexibility according to different sizes of the vehicle

• small dimensions

• diminished difficulty and the price of installation

Here is an implementation example related to Figures 1-7, that represent:

Figure 1 - the block scheme of an audio system for vehicles, according to the present state of technology Figure 2 - the electrical scheme of the type B cables that feeds passengers' area loudspeakers, according to the present state of technology;

Figure 3 - the block scheme of the distributed audio system that is installed on-board of a vehicle, according to the invention;

Figure 4 - the block scheme of the distributed audio system's Connector module, installed on-board of a vehicle, according to the invention;

Figure 5 - the block scheme of the vehicle driver's Microphone module of the distributed audio system, installed on-board of a vehicle, according to the invention;

Figure 6 - the block scheme of the audio Amplifier module of the distributed audio system, installed onboard of a vehicle, according to the invention;

Figure 7 - the block scheme of the Radio FM/AM/DAB module of the distributed audio system, installed on-board of a vehicle, according to the invention.

The distributed audio system, installed on-board of a vehicle, according to the invention, consists of several vehicle distributed modules. These modules are chain connected using a single unshielded cable 1, with a single pair of twisted UTP wires, using A2B technology developed by Analog Devices Company, for the interconnection of different audio equipment. Such a system is presented in Figure 3, any configuration along the chain being allowed, except the Connector Module MC that needs to be interconnected with the device that controls the functioning of the system, according to the invention and which usually is an on-board Computer C. This is the reason why the Connector Module MC is always at the end of the chain where the on-board Computer C is. Audio Amplifier Modules A are distributed in different areas: the driver's cabin, the external loudspeaker/loudspeakers area, only if they are required, and several areas in the passenger's lounge, depending on the length of the vehicle. These modules feed the loudspeakers D in that particular area with audio signal. This way, no matter the size of the vehicle, both choosing the maximum total necessary amplifying power and the level of the delivered signal at a certain time for each area are possible, correlated to the measured environmental noise in that area. Moreover, considering that the audio Amplifier modules A are close to the loudspeakers D that they feed, the type B cable dimensions are significantly reduced, so that the difficulties and the cost of installation decrease. As a result, type A cables are not used and the type B cables are significantly shortened. The type C cables are also shortened because the distance between the board of the vehicle and the driver's microphone is very short, compared to the distance from the board of the vehicle and the classic audio system, which is usually installed into a special equipment niche. Moreover, the type C cables are not necess O 2023/059214,_{omrna nc}|_s that determine the way the audio system wor?CT/R02022/050009_n the console of the on-board Computer C, which usually is very easy accessible for the driver, and not using on-board physical switches.

The modular distributed audio system consists of several types of interconnected modules: the Connector module MC, the driver's Microphone module MF, the audio Amplifier modules A, the Radio FM/AM/DAB module R. The system is not closed and allows adding new types of A2B technology compliant modules. An audio system comprises only the necessary modules, customized for the client's needs, depending on the type of vehicle and resulting in an adaptation of the cost to the necessities. Below the functionalities and the way of providing the aforementioned modules are described.

The Connector Module MC. This module is unique and the only mandatory one in the chain of the audio system and provides its connection to the on-board Computer, the one that provides both the automated location-dependent audio content and the control of the functioning of the audio system, according to the invention. The connection between the Connector module MC and the on-board Computer C is achieved via a USB interface or via an Ethernet interface. The downstream connection to the other modules is achieved via a UTP cable 1, which stands for the aforementioned A2B's "bus".

See the block scheme of this module in Figure 4. The Connector Module MC consists of an USB/Ethernet interface component 2, an A2B type Master transmitter/receiver 3 (according to Analog Devices technology) and a non-volatile memory 4.

The USB/Ethernet interface 2 receives USB or Ethernet standard compliant signals from the on-board Computer C and provides as an output TDM audio signal that may include 8 or 16 digital audio channels, with a sampling frequency of 48 KHz and a maximum 32 bits resolution. The USB/Ethernet interface also receives configuration commands of the modules that form the distributed audio system, from the onboard Computer C, transforming them into I2C (Inter- Integrated Circuit introduced by Philips Semiconductors) compliant commands, which are then transmitted to the Master transmitter/receiver 3 via a 2 wired "bus", according to the cited standard. The following description the I2C commands are transmitted between different components of the system using this kind of "bus".

The TDM signal is transmitted to the Master transmitter/ receptor 3, which modulates it, according to the A2B technology, and sends it downstream to the other modules. These modules will extract their intended audio channels, according to the assigned software configuration for each of them. The I2C commands received by the Master transmitter/receiver 3 are also included (using the same A2B technology) into the downstream transmitted signal to the other modules, allowing to the send of commands to them.

The USB/Ethernet interface 2 works in the opposite way too, meaning that the TDM signal provided by the other modules, consisting of digital audio signals received from the microphones and other audio sources, via the Master transmitter/receiver 3, is converted into USB or Ethernet signals, that reach the on-board Computer to be processed.

The Master transmitter/receiver 3 is connected to a non-volatile memory that manages the identity of the Connector module MC.

The driver's Microphone module MF. This module consists of two microphones 5, 6, that receive the voice of the audio driver or, depending on the case, of the vehicle's guide, allowing both the generation of announcements to passengers and VoIP calls via the GSM modem contained by the on-board Computer C. The VoIP calls are handsfree calls, functionality achieved by the driver's Microphone module MF, together with the loudspeakers in the driver's cabin that are fed by a separate audio Amplifier module A, the vehicle driver's Microphone module MF, providing the necessary "echo cancellation" feature in this case. This module is connected both downstream and upstream in the audio system network via a UTP cable 1 with any of the other modules.

See the block scheme of this module in Figure 5. The module consists of an A2B Slave transmitter/receptor 7 (according to the Analog Devices technology) and an echo canceller block 8, named "Echo Canceller" according to international terminology. The Slave Transmitter/Receptor 7 facilitates the upstream and downstream connection with other modules of the audio system via a UTP cable 1. It controls the echo canceller block 8 via I2C commands. The management of the audio streams in the WO 2023/0592140 system by the vehicle's driver is achieved using swit PCT/R02022/050009 tside the module. These switches (9, 10 and 11) allow the setting of priorities, such as the priority of the driver's announcements related to the automated announcements provided by the on-board Computer C. These priorities are managed by the on-board Computer C. It needs to be noted that, as also stated above, these switches (9, 10 and 11), usually placed on the board of the vehicle, easy accessible for the driver, may not exist, and the management of the audio streams can be achieved by commands executed from the on-board Computer's C console.

In order to achieve driver's voice retrieval function, there are two microphones 5 and 6 that are connected to the echo canceller block 8. When the driver wants to make announcements to the passengers in or outside the vehicle, he keeps switch 9 pushed as it usually is a non-latching switch. In this case, the signal provided by the microphones 5 and 6 is processed and then delivered, via a digital signal, according to the I2S standard (Inter-IC Sound) and named l2S_0ut 12, to the Slave transmitter/receiver 7. With the help of the audio system chain, this signal is directed according to the vehicle driver's wish, using the latching toggle switch 10, to the audio Amplifier modules A, placed inside/outside the vehicle.

In order to provide handsfree VoIP calls, the signal gathered by microphones 5 and 6 travels the same way as stated above to the Slave transmitter/receptor 7, being redirected to the Connector module MC and from there to the on-board Computer C, via USB/Ethernet interface 2. The in-built GSM modem in the on-board Computer C receives this signal and transmits it via the GSM network to the vehicle driver's interlocutor, placed wherever in the GSM network access area. The opposite signal coming from the interlocutor's microphone reaches, via the GSM network, back to the on-board Computer's GSM modem and is transmitted to the Connector module MC via the USB/Ethernet interface 2. From here, via the audio system's A2B chain, the signal is directed to the Amplifier module A, that serves the driver's cabin loudspeakers and that allow the driver to hear the interlocutor's voice. Because the audio signal containing the interlocutor's voice and emitted by the driver's cabin loudspeakers will be also gathered, with a certain delay, by the microphones 5 and 6, together with the driver's voice, the interlocutor will hear a powerful echo of his own voice if additional cancellation measures are not implemented. This cancellation is accomplished by the echo canceller block 8. This block receives from the Slave transmitter/receptor 7 a copy of the audio signal that reaches the audio Amplifier A feeding the loudspeakers in the cabin, via l2S_ln signal 13. Using this signal, the echo canceller block 8 is able to cancel the supplementary received signal, with a delay, by microphones 5 and 6, delivering only the driver's voice, via l2S_0ut 12, to the Slave transmitter/receiver 7 and further to the on-board Computer's modem, cancelling the upsetting echo. The echo canceller block 8 is controlled by the on-board Computer C via I2C commands received via the Connector module MC.

To allow the directing of the audio signal produced by the FM/AM/DAB Radio module R to the driver's cabin and/or to the passengers inside the vehicle, the driver uses another latching-toggle switch 11.

The Amplifier module A. This module consists of a digital amplifier 14 and a digital environmental microphone 15. The number of such modules in the audio system chain depends on the size of the vehicle, each covering a certain area, both inside and/or outside the vehicle. The total power of the audio signal related to the whole vehicle is achieved by installing the suitable number of these modules. This way, the modular distributed audio system is adapted to the size of the vehicle.

The amplifier 14 feeds the loudspeakers in the proximal area with A2B chain received audio signal, resulting in the diminished length of type B cables. Microphone 15 is meant to gather environmental noise, which is then transmitted via the Slave transmitter/ receiver 16 and the audio system's A2B connection chain to the on-board Computer C, in order to be processed and measured. Based on this measurement the level of the audio signal is regulated in the area covered by loudspeakers D connected to the module. This way an optimal audition is obtained for each area of the vehicle. This module is connected downstream and upstream to the audio system chain via UTP cable 1, with any of the other modules.

See the block scheme of this module in Figure 6. The module consists of a Slave A2B transmitter/receiver 16 (according to Analog Devices technology), a digital audio Amplifier 14, a digital environmental microphone 15 and a non-volatile memory 17. The Slave transmitter/receiver 16 is connected upstream and downstream to other modules of the audio system via UTP cable 1. It controls the digital audio Amplifier 14 via I2C commands.

The digital audio Amplifier 14 receivesTDM audio signal from the Slave transmitter/ receiver 16 and using the same device receives the I2C command from the on-board Computer regarding the audio channel that is to be amplified and provided at the output to the loudspeakers. The digital amplifier 14 receives, via I2C also, the command that sets the audio signal level delivered to the loudspeakers.

The digital microphone 15 gathers the environmental noise level that gets to the on-board Computer C via the Slave transmitter/receiver 16 and, depending on this level, calculates the optimal level for the signal delivered to the loudspeakers D, corresponding to the environmental microphone's area.

The transmitter/receptor 16 is also connected, via I2C, to the non-volatile memory 17 that manages the identity of the audio Amplifier module A.

The FM/AM/DAB Radio module R. This module provides the reception of FM/AM analogue and digital DAB radio broadcasts and inserts them into the audio system's chain. This way, this audio content can be distributed to both the vehicle driver and the passengers, by the driver's latching-toggle switch 11, connected to the vehicle driver's Microphone MF. This module is connected both downstream and upstream to the audio system's chain via UTP cable 1, with any of the other modules. The graphical interface that allows using this module is provided by the on-board Computer's console C. This module can be installed close to the FM/AM/DAB antennas in order to obtain the shortening of the connecting cables or even their complete removal. It is worth noting that these coaxial type cables are also expensive and that this way of mounting reduces the cost of both the cables and their installation.

See the block scheme of the FM/AM/DAB Radio module R in Figure 7. The module consists of a Slave A2B type transmitter/receiver 18 (according to the Analog Devices technology) and an integrated FM/AM/DAB receptor 19 for the reception of the radio broadcasts in the standard frequency range with FM/AM/DAB modulations. The receptor 19 is controlled, regarding the working parameters (such as the selection of the working band, the type of modulation and the reception frequency), by the on-board Computer C, via I2C commands received from the Connector module MC and the Slave transmitter/receiver 18. The radio signal received by the receptor antennas 20, 21, and 22 (one for each band- FM, AM, DAB) is demodulated and processed by the receptor 19 and then transmitted as a digital audio signal, via the I2S interface 23, to the Slave transmitter/receiver 18 which redirects it to any of the Amplifier modules A, using the audio system chain. This way, the radio broadcasts can be listened by the driver and/or by the passengers inside the vehicle, by using switch 11.

Technology limitations regarding the distributed audio system

The distributed audio system can be built with a Connector module MC, connected to the on-board Computer C and one to maximum ten modules of the other three types, installed in any order, depending on the vehicle. The interconnection chain can have a total length of the UTP connection cables 1 up to 80 m, and a maximum distance of 15m between two modules. These limitations are imposed by the A2B interconnection technology. These limitations allow the use of the distributed audio system in all the passengers' transportation vehicles (buses, trams, trolleybuses) and even in low number of car trains.

Even if the invention is described here related to specific ways of implementation, different modifications and changes can be done without moving away from the purpose of this invention, as it is presented in the claims below. Consequently, the description and the figures must be seen more as an example than in a restrictive way and all these changes are meant to be included in the purpose of this invention. Any benefits, advantages or solutions to the problems described here regarding to the specific accomplishments are/are not meant to be interpreted as a necessary essential characteristic or an element of one or all the claims.

Claims

1. Distributed audio system installed on board of a vehicle, described by consisting of a Connector module (MC), a vehicle driver's Microphone module (MF), at least one audio Amplifier (A), a FM/AM/DAB Radio module (R) and an on-board Computer (C) distributed along the vehicle and chain connected by a single UTP cable (1), with a single pair of twisted wires, using a well-known technology, for the interconnecting different audio equipment, where:

° the on board Computer (C) controls, via a dedicated software, the whole system and provides the location-dependent automated audio content;

° the Connector module (MC) is interconnected with the on-board Computer (C) via an USB interface (2) or an Ethernet interface (2) and the other downstream modules, using an UTP cable (1), so that the Connector module (MC) is placed at the end of the chain where the onboard Computer (C) is, consisting of:

■ a USB/Ethernet interface component (2) that receives from the on-board Computer (C) signals according to the USB or Ethernet standards and provides as an output Time Division Multiplex (TDM) audio signals, that include 8 or 16 digital audio channels, with a sampling frequency of 48 KHz and a maximum resolution of 32 bits, and receives from the on-board Computer configuration commands for the modules that form the audio system, transforming them into I2C standard compliant commands and

■ a Master transmitter/ receiver (3) that modulates the TDM signal and transmits it downstream to the other modules, that will extract the audio channels intended forthem, according to the software configuration assigned to each of them, using the I2C commands received by the Master transmitter/receiver included in the signal downstream transmitted to the other modules, allowing commanding them.

° The audio Amplifier modules (A) are area distributed: the driver's cabin, the external loudspeaker/loudspeakers areas and several in the passenger's lounge, depending on the length of the vehicle, each module A containing:

■ a digital amplifier (14) and a digital microphone (15), where the amplifier (14) feeds the proximal loudspeakers (D) with the audio signal received via the audio system chain and the microphone (15) has the purpose of collecting the environmental noise, which is then sent via the connections chain to the on-board Computer (C) to be processed and measured; based on these measurement, the level of the audio signal in the area covered by the loudspeakers (D) connected to the module is regulated, resulting in an optimal audition in each area of the vehicle;

2. Audio system, according to claim 1, described by the fact that the TDM signal is transmitted to the Master transmitter/receiver (3) in the opposite direction too, meaning that the TDM signal coming from the other modules, consisting of digital audio signals received from microphones and other radio sources, is converted in USB or Ethernet signals that reach the on-board Computer (C) to be processed.

3. Audio system, according to claim 1, described by the fact that the vehicle driver's Microphone module (MF) consists of:

• a Slave transmitter/receiver (7) that connects upstream and downstream with other modules of the audio system and controls an echo canceller block (8) via commands

• several switches (9, 10 and 11) that provide the driver's audio streams management in the distributed audio system and allow the setup of priorities

• two microphones: (5) and (6) used for vehicle driver's voice collection, connected to the echo canceller block (8), for passengers announcements, and the echo-free vehicle driver's voice collection in order to achieve proper handsfree GSM calls.

4. Audio system, according to claim 1, described by the fact that the audio Amplifier modules (A), also consist of:

7 • a Slave transmitter/receiver (16) that connects upstream and downstream with other modules of the audio system via UTP cable (1) and controls via commands a digital audio amplifier (14);

• a digital audio amplifier (14) that receives the TDM audio signal from the Slave transmitter/receiver (16) and from the on-board Computer (C), via the same device, the command regarding the audio channel that is to be amplified and to provide it as an output to the loudspeakers (D) and the command that decides the level of the audio signal delivered to the loudspeakers (D)

5. Audio system, according to claim 1, described by the fact that the total power of the audio signal regarding the whole vehicle is achieved by installing a custom number of such audio Amplifiers (A).

6. Audio system, according to claim 1, described by the fact that the FM/AM/DAB Radio module (R)also consists of:

• an integrated FM/AM/DAB receptor (19) that receives FM, AM and DAB broadcasts via several different antennas;

• a Slave transmitter/receiver that connects upstream and downstream with other modules of the audio system via an UTP cable (1) and controls the FM/AM/DAB receptor via commands.

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