The TR2070 is a basic Ground Loop Isolator, designed to electrically isolate audio devices from each other.
Hum in audio systems is usually caused by ground loops in the system. A common mode current will flow in a ground loop created by an electrical system that has grounds on different voltage potentials. This results in a 50 Hz hum in the audio signal.
The most common method to solve these problems is an audio isolation transformer such as the TR2070.
This makes the TR2070 a device which always need to be in reach for every audio technician.
When ground loop problems are encountered, these can be solved in a jiffy, by using the TR2070