To test a splitter for through loss, first measure and record the level of the signal source. Measure the signal level at the unterminated output port with the Frequency Selective Voltmeter. Before we begin testing, it's essential to understand how cable splitters work. The parameters listed here are typical values which may vary. To test a cable splitter, follow the steps below: Step 1: Disconnect all devices from the splitter Before testing the splitter, ensure that all devices that are connected to it are turned off and disconnected. I have two possible guesses on which splitter is mine, but I'd like to validate that without potentially disconnecting someone else's internet.