The RSD-EYE+ is a small and lightweight multifunctional handheld detection device for sensing pulse modulation from the power line communication (PLC) signal between the transmitter and RSD-X-PLC, to ensure compliance to the SunSpec Alliance Rapid Shutdown protocol. In addition, the RSD-EYE+ can also be used as a handheld transmit device, by connecting an optional external DC cable to send an in-line keep-alive signal to the RSD-X-PLC.