GNSS (GPS, GLONASS, BeiDou, Galileo) Controlled Multichannel Audio Player
Application: Automated audio-guided tours for sightseeing trains, busses & or boats with multiple language support.
The GNSS controlled multichannel MP3 audio player is intended for sightseeing vehicles that carry tourists through a mainly outdoor area (e.g. city). At each point of interest, a GNSS trigger point can be set to enable the play back of an associated voice/music announcement. The player works fully autonomously and thus relieves the driver from hazardous actions.
Separate stereo MP3 player modules with individual memory cards (microSD format) are available for each supported language. Typically eight stereo channels implementing eight different languages are adequate. The system consists of a hidden player box that contains the power supply (9 - 36 VDC) circuitry, the GNSS receiver and the MP3 player modules. An active GNSS antenna is included and should be mounted on the vehicle's roof, although in-vehicle antennas are also adequate. For monitoring purposes an internal audio multiplexer selects one of the channels and feeds it via an internal amplifier to loudspeaker terminals. The selected channel and volume can be adjusted with push-buttons.
The player box is connected to a control box at the driver's seat via a thin flexible and shielded 5-pole cable of up to 4m length. Via this control box, the driver can operate and monitor the audio players.
There are two modes of operation, push-button selectable:
- In GNSS mode audio tracks are played in a random order according to the current geographic postion of the vehicle
- In Manual mode the player is controlled by four push-buttons (play/pause, stop, next and previous track)
The current track number and the elapsed time are displayed in two 4-digit 7-segment LED displays. Up to 126 audio tracks can be accessed on each MP3 player with a latency of less than 100 ms.
The GNSS circuitry is able to track up 3 GNSS (Global Navigation Satellite Systems) simultaneously with up to 72 channels and a position update of two times per second. Furthermore it supports Untethered Dead Reckoning (UDR) with built in sensors (3D Gyroscope, accelerometer) to significantly improve the position accuracy in poor GNSS signal reception areas (urban canyons, short tunnels, under trees, etc.). Useful positioning data is even available during periods of complete signal loss and this without the need to connect any external sensors. The system works without local maps and can be used in all geographic areas with adequate GNSS reception.
The operator himself can easily program the GNSS trigger points by driving along the route and storing the desired positions under push-button control. All positions are stored in a non-volatile flash memory inside the control unit. A variety of triggering options like "trigger on entering a zone", "trigger on leaving a zone" or "trigger track X only if previous track was Y" etc. can be implemented to cope with complex routes with overlapping segments.
The system is available in two versions:
- The analog version outputs the audio signals as 8 separate stereo line outputs (0,75Vrms) at the rear SUB-D37 pin connector. An external analog multiplexing system must then be used to connect the seat units.
- The digital version multiplexes the 8 audio channels to a single digital line (optical or electrical) that can directly feed the required number of seat units by daisy-chaining either plastic optical fibres (POF) with Toslink connectors or CAT5e patch cables with RJ45 connectors through each seat unit.
The digital version works in conjunction with the "Multichannel Digital Audio Distribution System" as shown in the picture below. The corresponding Seat Unit consist of a PCB/Frontpanel assembly for flush fit mounting
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