Bosch Appliances 9922 141 70691 en manual Acoustic feedback

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DCN Wireless Installation and User Instructions System Design and Planning

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8.7Acoustic feedback

Acoustic feedback (‘howling’) occurs when the sound of the loudspeakers or headphones in the system is sent to the system again by activated microphones.

table 8.1: Acoustic feedback

Source	Quick solution	Structural solution
The acoustic feedback is caused by	Decrease the volume level of the	Do as follows:
the loudspeakers of the contribution	system. For example, with the knob	1 Install a feedback suppressor
devices.	on the front of the central control	between audio input 2 and audio
	unit (refer to section 10.6.3).	output 2 of the central control
		unit.
		2 Set the audio routing mode of
		the system to Insertion (refer to
		section 12.6).

The acoustic feedback is caused by	Decrease the volume level of the	Install a feedback suppressor
an external public address system	public address system or the DCN	between audio output 1 and the
that is connected to the DCN	Wireless digital congress network.	input of the external public address
Wireless digital congress network.		system.

The acoustic feedback is caused by	Tell the chairmen and the delegates	Install and configure the
the headphones that are connected	to decrease the volume level of their	headphones level reduction of the
to the contribution devices.	headphones with their contribution	contribution devices. (Refer to the
	devices.	section about the contribution
		devices.)

Bosch Security Systems 2007-02 9922 141 70691 en

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Contents DCN Wireless Page Important Safeguards Disclaimers Signs About this manualFunction Digital version Admonitions and notesConversion tables Electro-static dischargesTable of Contents 10.1 105 Intentionally left blank System Design and Planning Limits Wireless network designFrequency band IntroductionGHz 400 412 417 422 427 432 437 442 447 452 484 GHz Calculation tool DCN designConcepts Control capacity Power capacityDCN power supply DCN-WCCU Power suppliesCable lengths DCN-EPS DCN-WCCUCable lengths ExamplesExample with interpreter desks DCN-IDESK Interpretation devices Interpreter booths with LBB4114/00INT-TX041 INT-TX082 INT-TX164 INT-TX328 PRS-4DEX41 Optical network designNodes DCN-CCU2 DCN-WAP1Cabling Power supplyDefinitions Cable couplers Optical fiber lengthMaximum cable length Bending Example layoutsCoiling Extended optical network Basic optical networkRedundant cables Redundant optical network with tap-off Tap-offsCamera control Infra-red wireless language distributionScenarios Public areas and walkways Headphones/headsetsInterpreter booths CobraNet User set-upDevice set-up Acoustic feedback Acoustic feedbackTransmission links Technical dataSystem electrical and electro-acoustic characteristics GeneralCombined devices from input to output SafetyEnvironmental conditions Combined devices from input to outputElectromagnetic compatibility Wireless devicesWireless devices Electro-magnetic compatibilityMiscellaneous MiscellaneousIntentionally left blank Central Devices Controls, connectors and indicators DCN-WCCU Wireless Central Control UnitFront view Rear view Internal settingsInternal settings 10.3.3 RS232 configuration Watchdog Internal back-up batteryGround Fuses InstallationExternal connections Voltage selectorLED 10.5.2 DCNOptical network 10 DCN connectionAudio inputs HeadphonesXLR Audio outputs 14 Audio input details, line level signals16 Audio output details Fault contact19 RS232 ports 10.5.8 RS232 portsWAP Configuration menuCCU 20 VU meter Navigation and operationTo select a parameter Bosch Security Systems 2007-02 9922 141 70691 en Main Fault status21 Messages low to high importance DCN-WCCU Enquiry 22 Monitoring sub-menu * = default23 DCN-WCCU Enquiry sub-menu * = default MonitoringDCN-WAP Enquiry 24 DCN-WAP Enquiry sub-menu * = defaultPTT Setup25 Setup sub-menu * = default NOM27 Loudspkr sub-menu * = default 26 Setup sub-menu * = defaultLoudspkr Intercom Wireless28 Intercom sub-menu * = default 29 Wireless sub-menu * = defaultDe-init Defaults30 De-init sub-menu * = default 31 Defaults sub-menu * = defaultFirmware DCN-WAP Wireless Access PointWall or ceiling 11.4 Installation11.4.1 General Logo TripodSystem ID ConfigurationPower values Power valueCarrier CC B a OperationMenu of the central control unit is open. Use these menu Initialization System configurationSystem Wireless modes 12.4.4 PTT Microphone modesOpen OverrideAudio routing modes Repetition rateRecorder Insertion Equalized PAFloor distribution Erase requests-to-speak and speakersMix-minus Location of the chairman IntercomLocation of the operator Start the system System operationStop the system Contribution Devices Bottom side DCN-WDU Wireless Discussion Units14.2.1 Top Left and right sidesDCN-WD DCN-WDD DCN-WDV Side views Microphone sensitivity Microphone sensitivityHeadphones level reduction Volume restore functionChairman ProcedureModes Single delegateSingle delegate with auxiliary control Dual delegateRemove microphone buttons Microphone buttons10 Install microphone buttons BatteryRims SubscriptionErase the subscription Headphones sockets, detailsQuick reference card External power supplyActivation DeactivationStatus LEDs Attendance LEDAttendance LED Compatible devices DCN-MICL, DCN-MICS Pluggable MicrophonesTypes and lengths Electrical and acoustic propertiesMicrophone plug, connection Battery capacity DCN-WLIION Battery PackCapacity LEDs Battery pack containers Hold DCN-WCH05 Battery ChargerWall Installation, wallInstallation, multiple battery chargers Power inletCharge level LEDs Loop-through socketElectrical properties DCN-WPS Power Supply AdapterDual delegate interface DCN-DDI Dual Delegate InterfaceInput adjustment switch * = default Input type switch * = defaultSignal level switch * = default DCN-FHH Ambient microphoneIntercom handset 19.6.1 DCNDCN connections Connections Audio inputsCmrr DCN-WFCCU Flight Case for DCN-WCCU DCN-WFCD10 Flight Case for Wireless Discussion UnitsIntentionally left blank Appendices Table A.2 Analog outputs Audio levelsTable A.3 Monitor Table A.6 Dual delegate interface DCN-DDIProduct index Central control unit wirelessCentral control unit wireless UL Extension power supply DCN Next GenPower Supply Adapter Wireless discussion unitWireless dual discussion unit Wireless discussion unit with votingStatements for FCC & Industry Canada Declarations DCN Wireless Installation and User Instructions Appendices Page Page Page Page Page Page Page For more information visit