The Qx from Intellijel is an expansion module for the Quadrax module from the same company. It expands each of the four channels of the main module by one End-Of-Rise and End-Of-Fall output each. Thus it is possible to combine the four function generators of the Quadrax to a gigantic, multi-level envelope, to switch other modules like sequencers step by step with the phase outputs or to trigger further envelopes.