Internet Calling; Logic - Shure SCM820 Digital IntelliMix Manual

Internet Calling

Dante-enabled mixers integrate software applications such as Skype
Lync , Voice. This enables multiple microphones to participate in a
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teleconferencing event.
1. Reference the Installation section to properly connect and setup
microphones to the mixer back panel.
2. Open the IntelliMix tab of the GUI.
3. Select Dual Mixer operation.
4. In the GUI, route channels 1 - 8 to Mix A only (deselect routing to Mix B).
5. In the Inputs tab of the GUI, route the Aux to Mix B only.
6. Open Dante Virtual Soundcard and turn it on.
7. Open Dante Controller (DC) software.
8. In DC, route the SCM820 tx channel 'Mix A' to computer rx channel 1.
9. In DC, route computer tx channels 1 and 2 to SCM820 rx channels Aux L
and R.
10. Connect Mix B analog output to a speaker or output device.
11. Open the computer's settings and select Dante as the input and output
soundcard.
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Logic

The logic functions of the SCM820 expand the mixer's range of installation
and control options. These functions can be hardwired or configured in the
GUI.
The following hardware logic functions are available for each channel:
Gate Out
Follows channel gating and goes to logic "low" (sinks current) when
microphone is gated on. 500 mA of current sinking ability is provided.
Mute In
Applying logic "low" (from GATE OUT or a switch closure to logic ground)
gates channel off (channel output is fully attenuated).
Override In
Applying logic "low" (from GATE OUT or a switch closure to logic ground)
forces channel on. When both Mute and Override are activated, Mute
takes precedence.
Logic Ground
Logic ground is distinct from the SCM820 audio ground. Make all logic
ground connections to this pin, including power supply ground of external
logic circuitry. To avoid switch clicks, do not connect logic ground to audio,
chassis or rack grounds.
Suggested Logic Application
This section contains suggestions on the uses of the SCM820's logic
capabilities. For additional suggestions and solutions to installation
problems, contact Shure's Systems Support.
Cough Button
The talker can turn off his or her microphone during coughing or private
conversations by installing an SPST pushbutton switch between the MUTE
IN and Logic Ground pins for each channel to be modified. When a channel
is muted, no audio is passed.
Set the mute control to post-IntelliMix setting (
> ) to ensure that unwanted sounds do not gate on other
Mute Control
microphones.
Chairperson-Controlled Muting
The chairperson can, by activating a switch, silence all other microphones
and be heard without interruption.
1. Set the desired channel to Chairperson Mute to manual (
> >
IntelliMix Panel Chairperson Mute
2. Connect the switch to the Override In logic connection for the
chairperson's microphone.
An alternative to a switch is to set the Chairperson Mute to Auto. In this
setting, when the chairperson's microphone activates, all other microphones
mute automatically.
,
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>
GUI IntelliMix Panel
>
GUI
).
Remote Channel-Open Indicators
Remote indicators can be used to indicate when a talker's microphone
is on. Connect the LEDs and a 5-volt supply to the GATE OUT pin. To
avoid switching clicks in the audio output, do not ground the power supply
negative terminal in the audio system or rack ground.
Important: If a single cable is used for the microphone audio signal and the
LED dc power, separate shielded pairs must be used. Failure to carry the
DC power on a shielded pair may result in audible clicking due to capacitive
coupling between the DC power lines and microphone lines.
Disabling the Gating Function (Always On)
Select Always On for the channel(s) that should remain open (
> .
IntelliMix Panel Always On
Inhibiting Gating for Unwanted Sounds
The MaxBus operating principle ensures that the mixer will activate only one
microphone per sound source. Muting a microphone channel prevents its
audio from appearing at the mixer's output. However, the muted channel set
to Post-IntelliMix still communicates with other mic channels via MaxBus.
A sound source picked up by a muted microphone will not activate other
microphones.
Sound sources that may cause unwanted microphone channel activation
include:
• A noisy fax machine or printer
• A squeaky door
• An intercom system
• A teleconferencing loudspeaker
The SCM820 can prevent these and similar sounds from activating
microphones by taking the following steps.
1. Place one microphone near the unwanted sound source. Connect that
microphone's signal to a channel input.
2. Mute the channel.
3. Set the Mute Control to Post-IntelliMix (
4. Adjust that channel's gain control just to the level where other
microphones in the system do not activate for the unwanted sound. If the
channel gain is set too high, other system microphones will be difficult to
activate for desired sounds. If set too low, unwanted sounds will continue
to activate other microphones.
Loudspeaker Muting
Some applications require a loudspeaker to be placed near each talker
to provide audio reinforcement, or to permit telephone conversation or
conference monitoring. Each loudspeaker can cause feedback unless it is
automatically switched off when the talker near it speaks. To provide this
function, connect the GATE OUT terminal of each channel to a separate
loudspeaker muting relay.
NOTE: A diode across each relay coil is required to suppress inductive
voltage spikes which may damage the SCM820.
An alternative to creating a circuit is a Logic Controlled Relay, such as the
Radio Design Labs (RDL) ST-LCR1.
"Filibuster" Mode
In normal operation, when several people talk, each microphone gates on
so that no speech is missed. In "filibuster" action, a microphone that is gated
on prevents other microphones from gating on. Once a microphone has
gated on, other microphones cannot gate on until the talker has paused long
enough for that microphone to gate off. Thus the person talking has the floor
and cannot be interrupted.
Set the maximum number of open microphones to 1 (
>
Mix A/B Max NOM
>
GUI
> > ).
GUI IntelliMix Tab Mute Control
> >
GUI IntelliMix Panel
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