The optical mux/demux motherboards occupy slots 0 and 1 of the Cisco ONS 15540 chassis. The chassis uses one optical mux/demux motherboard for unprotected operation or two per system for protected operation. Each mux/demux motherboard can accept up to four mux/demux modules. The modular mux/demux motherboards are available with or without OSC (optical supervisory channel) and can be populated according to user needs.This motherboard supports mux/demux modules without OSC.