The Roland S-4000M is a REAC merge unit that allows you to merge multiple REAC devices to enable a whole new world of configurations. The S-4000M merges up to four Digital Snake heads, such as the S-0808, S-1608 and S-4000 series, and merges the input/output to a single REAC signal. Ports 1 to 4 supply REAC embedded power to compatible products such as the S-0808. The intelligent Auto Map function assigns input channels automatically. REAC master devices recognize the S-4000M as a single REAC slave unit even when multiple digital snake heads are connected.

The S-4000M also serves as a distributor of outputs and/or splitter. Any inputs returning from Port A (Master) are distributed to the outputs depending on the devices connected. When S-0808s are connected, specific output assignments can be set. The M-400/M380 V-Mixer or dedicated PC Remote Control Software (S-4000RCS) configures routing, input gain, PAD and phantom power.