These Chassis controls up to 16 switch modules with 9 to 25 wires switched per module. They are basically used to make a 9 to 25 wire 1x16 mux with D9, D15 or D25 connectors. LEDs on the front panel show switch and power status. Add up to 16 Switch Modules and a Control Module to complete the system. Push button manual control on the front panel is optional.