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Biamp Systems

Connecting a Shure MX395-LED to a Logic Box

One popular application for the Logic Box or Voltage Control Box is to interface with conferencing microphones that feature mute switches and LED indicators, and Shure is a leading manufacturer of such microphones.  This article describes how to physically connect a Shure MX395-LED microphone to a Biamp Logic Box.


After completing the steps in this article, you will be able to connect a Shure MX395-LED to a Biamp Logic Box.  This will allow your Audia or Nexia configuration to control the LED's on the MX395-LED.

Note that Shure MX series microphones use phantom power to power its LED's.  Therefore, no external power supply is required for this application.


The Shure MX395-LED is a boundary microphone with a bi-color LED ring.  The MX395-LED comes with a 5-pin XLR connector.  The pinout of this connector is shown in the table below:

XLR Pin Function
Pin 1 Audio Ground
Pin 2 Audio -
Pin 3 Logic Ground
Pin 4 Audio +
Pin 5 LED In


The audio conductors on the microphone will connect to the audio inputs on the Audia/Nexia like a typical microphone.  The LED and Logic Ground conductor will connect to the Logic Box.  The LED In conductor connects to a logic output, and the Logic Ground connects to any of the ground terminals on the Logic Box.

Each MX395-LED uses one logic input terminal on the Logic Box, which means that a maximum of 20 MX395-LED's can be connected to a single Logic Box.  The diagram below shows a typical wiring scheme for a single MX395-LED:


LED control

The microphone's LED ring will light up green when there is less than 1V across pins 3 and 5 (i.e., logic output in the low state), and it will light up red when there is 5V across pins 3 and 5 (i.e., logic output in the high state).

Further reading

Once the device is physically connected to the Logic Box, you'll need to program it.  See Logic Box Programming for more information.

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