Say you’re at an Office and you come across a jack that needs to be traced but it is Active. A Toner wouldn’t work for this so you would need a device that can send a Beacon to make the light on the Network Switch Flash/Pulse. Those type of testers costs an arm and a leg. However there is a free way so to speak on making a Laptop act as a Beacon.
Chances are the Laptop is running Windows. You can run a simple BATCH script to make the NIC send a Pulse/Flash so to speak.
netsh interface set interface name="Local Area Connection" admin=disabled
netsh interface set interface name="Local Area Connection" admin=enabled
How this script works is very simple. It just makes the NIC on the Laptop to enable and disable. Doing so makes the Switch flash on and off every couple of seconds as the script runs.
You could also slap together an Arduino with an Ethernet Shield to do the same thing and have a dedicated device.