FMT-400-BUS-S Rack Extender Slave Module provides connectivity to master rack containing the 400-CPU module, and the 400-BUS-M. 

• Up to a maximum of 15 extension racks can be connected to the main rack using 400-BUS-S modules
• Maximum distance between each rack - 40 metres
• Compatible 400-CPU modules: 400-CPU-B, 400-CPU-C in main rack connected to 400-BUS-S via a 400-BUS-M and optical fibre
• Only the 400-CPU-B and 400-CPU-C support extn racks, and so only they can use the 400-BUS-M

See Datasheet [405KB]