This ID telephone tester is designed for home and office use. It accurately identifies and displays incoming call information, with a maximum of 8 digits and 57 groups for , and 12 digits and 44 groups for . It requires connection to a telephone line to function and has a sleek and simple design that is easy to use. Features -Color:Black -Material:PVC -Size:13.00X5.00X2.00cm/5.11X1.97X0.79in -Automatic identification and display of / incoming call information - maximum 8 bit 57 groups, 12 bit 44 groups - maximum 8 bit 65 groups, 12 bit 49 groups -Accurately detects: The device accurately detects and shows incoming call information using / technology -Easy to use: Rational design, easy to operate, easy to install and use -Functionality: The device needs to be connected to a telephone line in order to function properly -Stylish appearance: Its sleek and simple design makes id telephone tester easy to use -Wide range of application: This id telephone tester is suitable for both home and office use Package list: 1 1 x replacement line 1 x instruction manual