It is an Audio Splitter for microphone signal used for distributing this signal into several identical outputs with the same level. Thanks to its transformer insulation, each output is isolated from others, avoiding ground loops. This is a very important issue as connected devices can have different ground references.
A Mic Splitter offers a direct output for Phantom feed from console and then can distribute an electrostatic microphone signal. Thus, one console cannot damage another device because a transformer does not transmit the direct current signal (DC) such as phantom power.
Also, microphone splitters usually incorporate transformers protected by a Faraday Shield. This protects against noise from electrostatic interferences, an issue particularly relevant for low-level signals like the microphone signal.
The microphone splitters are typically passive audio splitters so if you need a line-level signal, a microphone preamplifier is required before distributing it.
