The unit worked flawlessly on day one. Allowed me to quickly trace some CAT5 cables around my new home. The next morning I tried again but the sending device kept disconnecting after 10-15 seconds. I thought I left the power on so I replaced the batteries. There are no dice. Tried different test modes etc. There is no cube. After it turns off, pressing the "Test" button or changing the switch mode will not restart it. You have to press the PWR button for it to work. and then turns off after 10-15 seconds. Same goes for the other reviewer. Raven called. send replacement. Let's see if it works. Update. Got a new device. Exactly the same problem. Send back. I should have known better. look elsewhere