543E Output Mixer Aux-Expander

Effect sends and returns for the 543 or 543CP mixers

The 543E expander features one effect send. Each channel strip of the 543 / 543CP mixer can be fed to the module with individual level. Knobs and CV inputs are available for volume control. After signals got processed externally, they can be routed back into the modular system via left and right return channels. Here, you’ll find potentiometers and CV inputs for altering the level as well. Several 543E expanders can be combined. Thus, you can add any number of effect sends and returns to your 543 or 543CP output mixer.
connectors

FX Send audio output
Four FX Send CV inputs
Two FX Return audio inputs (L / R) Two FX Return CV inputs

http://www.lunar-experience.com/download/543e.pdf