FMM-1 is a standard-sized module (typically mounts to a 4" [10.16 cm] square box) that supervises either a Class A (Style D) or Class B (Style B) circuit of dry-contact input devices.
The DOM4-8 is the central control element of the Variodyn D1. It is equipped with 4 independent audio outputs to access 4 channels, and operates 2 zones (8 circuits total).