What is SIMPLINK? With a single remote control, you can easily manage various devices such as a soundbar or set-top box connected to a projector with HDMI. Know more via this LG HU915QE Projector SIMPLINK using guide.

Using SIMPLINK steps
With Up to three devices can be connected and used simultaneously.
1. Connect the SIMPLINK HDMI Output port to the projector’s HDMI IN port with
an HDMI® cable.
2. Select (Q. Settings) → [More Options] → [General] → [Devices] → [HDMI Settings].
3. Set [SIMPLINK (HDMI-CEC)] to [On].
4. Turn on the connected device. When the projector automatically connects to the device, the input will switch. If the device is not automatically connected to
the projector, click the button.
• This feature works only with devices with the logo. Check for the SIMPLINK logo on the external device. There may be a problem using the device if the device does not meet the required specifications.
• A high-speed HDMI® cable with CEC (Consumer Electronics Control) function is required to use SIMPLINK. Pin 13 of the high-speed HDMI® cable is used for data transfer between devices.
• If you want to output sound to the external audio equipment connected through the HDMI cable, set [SIMPLINK (HDMI-CEC)] to [On].

Read more:
LG CineBeam HU915QE Projector Overheating Prevention Tip
How to Connect Slimport Device to LG CineBeam HU915QE Projector?