Features: <br> <br>Perfect for safely troubleshooting and testing audio systems. <br>This phase meter can test all speakers of all car, such as small treble, door speakers, subwoofer, etc. <br>Low battery light on indicates that the battery power is low. <br>Effectively used to test speaker polarity. <br>Professional manufacturing, high reliability. <br> <br>Specification: <br>Condition: 100% Brand New <br>Material: Plastic <br>Color: Black + Silver <br>Size: As Picture Shown <br>Built-in Battery: 1 x 9V 220mAh battery <br>Package Weight: Approx. 139g/4.9oz <br>#How to use the tester? <br>the CD with the package include 4 section test music. <br>section 1: left channel noise signal <br>section 2: right channel noise signal <br>section 3: phase test signal <br>section 4: same as section 3 <br>Put it in car cd player, and play section 1 or 2, check if left/right channel connection is right. <br>Play section 3 or 4, the sound speaker will produce a fixed frequency signal, then press test button. <br>3 green light flash and 1 red light indicates that the speaker output is in positive phase correct connection); 3 red light flash and 1 green light indicates negative phase (reversed connection). <br> <br>Package List: <br>1 x Phase Meter <br>1 x CD<br>1、Perfect for safely troubleshooting and testing audio systems. <br>2、This phase meter can test all speakers of all car, such as small treble, door speakers, subwoofer, etc. <br>3、Low battery light on indicates that the battery power is low. <br>4、Professional manufacturing, high reliability. <br>5、Effectively used to test speaker polarity.