Pricom Pricom made a very nice DCC protocol analyzer with an LCD screen. http://www.pricom.com/Trains/DCCTester.shtml Apparently no longer sold because of lack of the LCD screen. You can update the firmware yourself, using a special cable: Wiring for firmware update cable. description RJ11 DB9 color NC 1 ground 2 5 yellow xmit > pc 3 2 brown rcv < pc 4 3 red ground 5 5 yellow NC 6 current and last firmware version: v1.52 Download page for the Pricom tester If you find one, buy it. NCE also makes a packet tester, see the NCE page.