These Chassis are typically used to control relays greater than 8x1 or control multiple relays in series forming larger switches than normally possible such as 16x1 to 32x1 sections. Or control mixtures of 8x1"s, 4x1"s, 2x1"s and 2x2 modules in any combination or configuration for up to 256 relay drives. LEDs on the front panel show switch and power status. Add Switch Modules, display / driver modules and a Control Module to complete the system or simply buy the chassis wired out to D connectors to control your own relays. A manual control is optional.