The MCX-8 is an 8-zone output expander designed to increase the number of outputs of the MCR-308 wireless receiver. Up to three MCX-8 expanders, with eight "open collector" outputs each, can be added to the MCR-308 via a supervised communication bus. Dry contact outputs can be provided if needed, using the RL-8 relay module that converts 8 open collector outputs to dry contact outputs.

For maximum convenience, the expander modules can be installed either close to the receiver or at the control panel end, with a distance of up to 1 kilometer (0.62 mile) between the receiver and the expanders. The MCR-308 receiver continuously monitors the communication bus, issuing inactivity alerts in case the connection is interrupted.

The MCX-8's printed circuit board is enclosed in a plastic cabinet for easy installation and added protection. The base can accommodate one or two MCX-8 units, or an MCX-8 and an MCR-308 unit. For tamper protection, an on-board switch is activated when the front cover is removed.