WiiM Pro has a 12V trigger output with a current rating of 220 mA that can be connected to an amplifier with a 12V trigger input. This brings an amplifier out of standby mode when the music starts playing, reducing the time it takes to become active and output audio to your speakers.
WiiM Pro will raise the voltage on the 12v trigger rail when the music starts to play. It will lower the trigger's voltage two and a half minutes after stopping playback. Whether the connected amplifier acts on this immediately or has its own timeout to be enacted is down to the manufacturer and may vary.
The external DAC or amplifier can use a 12 V trigger to determine if the music starts or stops. Please check your device manual with trigger input for details.
Please turn on the auto-sensing of Line-in/SPDIF-in by selecting the Device tab -> Tap the device setting gear icon > Audio Input > Turn on Auto-sensing. It will detect whether there is a signal from Line-in/SPDIF-in input source and helps automatically raise and lower the trigger's voltage on the 12v trigger rail.