DISPLAY RANDOMLY TURNS ON AND OFF AFTER OPERATING HOURS I was the IT sysadmin for a Video Wall system in a busy mall. One night, I got a call saying one of the display screens kept turning on and off randomly. It was supposed to be off after hours, and I thought it might be caused by a short circuit (bec media player AC Power Loss Recovery is "on"). The electrical team checked and found no short circuit at all. I tested the media player and checked the logs, the Meraki switch which this media player is connected; logs says the same—it was definitely turning on and off at odd times. This freaked out tourists and employees waiting at the taxi stand after mall hours!   Finally, I discovered the source of the mystery: the screen power was somehow connected to a nearby elevator, and at night there is not enough power supply for all the devices. When the elevator was used, it drew a lot of current, causing a surge that triggered the screen to turn on and off; again and again. It was scary and funny at the same time, proving that sometimes tech troubles have surprising explanations!   ... View more