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The product you linked to is just a serial port expander (M1XSP). It will work fine with the EZ8 (I used to have an EZ8, and moved them, all 4, to the M1G when I upgraded). If you want INSTEON support, then you would need to get the correct interface, which attaches to the M1XSP. The M1XSP is designed to interface tons of hardware, including home automation protocol interfaces (so the M1 can support UPB, INSTEON, Z-Wave, X10, Centra-Lite, etc.), thermostats, W800RF X10 RF receiver, anything really that communitcates via a serial port. The serial device either has to support an ASCII protocol, or has to be supported by the M1XSP firmware.