What is the function of each pin on the MX395-LED model and the MX400SMP? Each has a five pin XLR connector.
Why is audio on pin 4 and pin 2?
Must phantom power be applied for the LED - be it green or red?
Based on development research for the MX395-LED and MX400SMP, RFI immunity improved when XLR pin 4 and pin 2 were used for the audio signal. +12 to +48 Vdc phantom power must be supplied to pin 2 and pin 4.
Pin 1: cable shield / phantom power return path
Pin 2: Audio - / phantom power supply path
Pin 3: Logic Ground for the LED
Pin 4: Audio + / phantom power supply path
Pin 5: Logic Input Control for the LED
Note 1: The LED operating voltage and current is provided by the phantom power.
A dim LED indicates insufficient current provided to pin 2 and pin 4.
Note 2: The microphone always sends an audio signal no matter the color state of the LED.
To have the LED lit as Green, leave pin 3 and pin 5 unused.
To have the LED lit as Red, connect pin 5 to +3 Vdc (or higher) TTL logic source; an example is the GATE OUT port on a Shure SCM810 or SCM820 automatic mixer. (Without a +3 Vdc difference between pin 5 and pin 3, the LED will remain Green.) To change back to Green, short pin 5 to pin 3, or remove the +3 Vdc TTL logic source. If using a 3 to 5 Vdc power supply in place of a TTL logic source, install a current limiting resistor (10,000 ohms, 1/4 watt) in series with the positive voltage lead.
Recommended cable type: a) twisted pair with a shield for the audio; b) a second twisted pair with its own shield for the logic; c) braided shield with >95% coverage.