The AIU4 is an 8 ohm speaker line to aux/mic level converter.
A 2 way terminal block is provided for easy connection to the existing speaker line.
The output is via an unbalanced 6.5mm socket and has a trim volume control.
Being transformer isolated helps eliminates earth loops and possible instability between the two PA systems.
The AIU4 is a passive device (no power required) and is housed in a compact plastic box.