XLR Splits are very useful things to have. They allow you to send a Microphone signal to more than one output. It is simply a "Y" adapter for XLR's in this most basic form.
Some people choose to use Transformers in one set of the sends, but I personally prefer a Transformerless version for the simple cost factor....Quality Transformers, such as Jensen, can easily turn an economical DIY undertaking into a several thousand dollar investment! A 16-channel XLR Splitter with 1 input and 2 outputs can be made for as little as $15.00 per channel; a Jensen Transformer will add about $50.00 per channel.
You can also wire an SPST ( Single Pole, Single Throw ) switch inline with 1 of these XLR Grounds to act as a ground lift switch.
I have not done this, so I didn't use it in the Graphic....I haven't tested it, so I'm not including it here. My policy is to only show that which I have done in these pages; that allows me to be certain that it works.

NOTE : If you use Phantom Power, make sure that it is only being used on 1 of your mixers if this is used in a FOH/Monitor Mixer Configuration.