1

I'm looking at the datasheet for a 'switching' XLR/Jack combo receptacle (NCJ10FI-V) but am unsure about how the switching works.

diagram from datasheet

Am I correctly assuming that S and SN form a normally open switch?

What if I want a microcontroller to be able to read whether a jack/XLR has been plugged in? Should I connect SN and GN to 5 V through a pull-up resistor, so they get pulled to ground when a connector is inserted?

Finally, what's the purpose of having 3 switches for the jack? To detect how far it has been inserted? I'm not sure how RN and TN would have to be wired up since connecting a pullup resistor to them would cause the signal to get distorted.

Application is audio input anywhere from mic level to over pro line level (-60 to +8dBu). With switchable phantom power.

Cedric
  • 427
  • 3
  • 10
  • Normally closed. They disconnect when you plug a jack plug in. Whether they also disconnect when you plug an XLR in should be in the datasheet. –  Sep 23 '21 at 16:33
  • @Theodore How would those switches 'know' if they're being pressed by a TRS vs a TS plug? – Cedric Sep 23 '21 at 20:35
  • @Cecemel You're right; they all switch at once. The benefit is only that they can be connected to different nodes when unplugged. – Theodore Sep 23 '21 at 20:40

3 Answers3

2

No, S and SN are normally closed, and the connection is opened when a plug is inserted. Note that S/SN, R/RN and T/TN work only with a TRS plug -- the only indication you get for an XLR plug is that G and GN are opened.

This type of jack is used in patch panels and similar applications. The idea is that if you plug something into the jack, it provides a signal to the S/R/T pins. But if nothing is plugged in, then an alternate source (the "normal" source), connected to the SN/RN/TN pins, is connected instead to S/R/T.

Dave Tweed
  • 168,369
  • 17
  • 228
  • 393
2

Based on the drawing, the SN and S form a normally closed switch, like all other switches.

Yes a GPIO pin with pull-up on SN and GND on S would work to detect an insertion of TRS plug.

There are three switches to allow for example signal passing through to speaker amp when no headphones are connected to TRS. Most likely other routing possibilities as well, like used as loop connector for effects.

Justme
  • 127,425
  • 3
  • 97
  • 261
1

The switches are in their normal position and they are "closed" (that is, conducting). S and SN will be closed (conducting) until you insert the jack.

What if I want a microcontroller to be able to read whether a jack/XLR has been plugged in? Should I connect SN and GN to 5 V through a pull-up resistor, so they get pulled to ground when a connector is inserted?

You can do that but will may get a loud pop as the tip and ring pass the contact.

Finally, what's the purpose of having 3 switches for the jack? To detect how far it has been inserted? I'm not sure how RN and TN would have to be wired up since connecting a pullup resistor to them would cause the signal to get distorted.

They can be used, for example, to disconnect the internal speakers when a headphone jack is inserted. In most cases the GND / sleeve connection would not be switched.

Transistor
  • 168,990
  • 12
  • 186
  • 385
  • How could I avoid the pop? – Cedric Sep 23 '21 at 17:45
  • What are you using it for? Audio? Input / output? Mic level, line level or headphone level? Add some info into your question. – Transistor Sep 23 '21 at 18:06
  • Done. I could delay activation of the ADC until after insertion is detected so the pop isn't captured. The 5 V spike won't be sent to the connected device, right? – Cedric Sep 23 '21 at 19:14