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Connecting a Shure MX412D or MX418D to an EX-LOGIC

One popular application for the EX-LOGIC 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 MX412D or MX418D microphone to a Tesira EX-LOGIC.

Note that even though this article shows diagrams for only the EX-LOGIC, the logic I/O terminals that are built into Tesira servers and TesiraFORTÉs can be used for the same purposes as an EX-LOGIC.


After completing the steps in this article, you will be able to connect a Shure MX412D or MX418D to a Tesira EX-LOGIC. This will allow your Tesira configuration to control the LED's on the MX412D/418D, and it will also allow the mic's mute switch to control functions within your Tesira configuration (like mic muting).

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

Conductor colors

The Shure MX412D/418D is a desktop gooseneck microphone with a mute switch and a single-color LED.  The MX412D/418D comes with a cable that is pre-terminated to a 3-pin XLR, with 2 additional logic conductors available inside the XLR connector housing.  The conductor color code for this cable is as follows:

Conductor Color Function
Red Audio +
Black Audio -
Green Audio/Logic Ground
Orange LED In
White Switch contact


The audio conductors on the microphone will connect to the audio inputs on the Tesira device like a typical microphone.  The LED and switch conductors will connect to the EX-LOGIC.  The LED In (orange) conductor connects to a logic output, and the Switch (white) connects to a logic input.

Each MX412D or MX418D uses two I/O terminals on the EX-LOGIC, meaning that a maximum of 8 MX412D/418D's can be connected to a single EX-LOGIC.  The diagram below shows a typical wiring scheme for a single MX412D or MX418D.


DIP switches

DIP switch 3 should always be in the UP position to ensure that the mic is not locally muted when the mute switch is pressed.  

If DIP switch 1 is in the UP position, the mute switch will behave like a toggle switch.  If DIP switch 1 is in the DOWN position, the mute switch will behave like a momentary switch.

LED control

The LED ring will light up when there is less than 1V across the orange and green conductors (i.e., logic output in the low state), and it will turn off when there is 5V across the orange and green conductors (i.e., logic output in the high state).

Further reading

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