NEW Redman CB 110 Volt Custom Workman TesterT-747 CB Microphone TesterT747 Mic and Echo Board Tester. Tests a large variety of microphones including most from RCI, Magnum, Cobra, President and Midland. There are spring loaded terminals on both sides of the tester so that you can easily connect and test noise toys and echo boards.The test center Also runs on 12VDC and has a standard 3-pin power cord jack as found on most CB radios.