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SHURE
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MX392 BASICS
The Shure MX392 is a surface-mount, electret microphone that includes a programmable
membrane on/off switch that can be controlled externally via logic input / output terminals. This
application note explores how to connect the MX392 to a Vortex device (EF2280, EF2241, EF2201,
EF2210, or EF2211) as well as how to program the Vortex device and MX392 to achieve the desired
control over the membrane switch.
The MX392 includes three extra conductors as part of the microphone cable:
• LOGIC GND (Green): Connects to the logic ground of the Vortex Device. This can be either
Pin 25 of the Logic Input port or Pins 21-25 of the Logic Output port.
• SWITCH OUT (White): Provides a TTL logic low when the membrane switch is pressed.
This signal is available at all times for all switch settings. The SWITCH OUT function
provides a momentary closure when S1 is OFF and a latching closure when S1 is ON. This
conductor will go to one of the Logic Input Pins of the Vortex Device (Pins 1-24).
• LED IN (Orange): This terminal draws 5 V DC. This function can be modified so that the
Vortex Device controls the action of the LED by flipping S3 to the ON position. If this
terminal is shorted to LOGIC GND, the LED turns on.
The MX392 includes a set of 4 DIP switches that are located on the printed circuit board of the
microphone. These DIP switches change the functionality of the membrane switch. For reference,
here is a list of all possible functions of the switch:
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