An external communication device, display device, display system, and control method therefor are disclosed. In accordance with an aspect of the present disclosure, an external communication device includes a wired communication module connected to a display device and configured to receive standby power; a wireless communication module configured to transmit a power application signal in response to reception of an event signal from at least one Internet of Things (IoT) apparatus via a wireless communication network according to whether the display device is active; and a communication controller configured to control an operation of the at least one IoT apparatus on the basis of a control command received via the wired communication module.