The RTD-RA can be part of an RTD-10 Duty/Standby network. A RTD-10 must be configured as Duty/Standby network master (see RTD-RA and RTD-10 installation instructions).
The master RTD-10 MUST be wired to an indoor unit, otherwise it will signal a fault and all units will run until it the fault is cleared - in this case the fault is only cleared when the RTD-10 establishes communication with an indoor unit via Daikin's wired remote controller P1P2 network.