Test Together: can be synchronized output control 4 servos. Accurate Test: used to compare the performance steering gear control of the steering servo output signal can be accurate to 2us (1 milliseconds = 1000 microseconds), you can test the steering gear is to respond to changes. PPM Signal: with PPM signal test function in the display, the input PPM signal changes while the input the PPM signal synchronization output to the servo Energized automatically enter manual mode (Manual) 20us 50H analog servo signal cycle, frequency 50Hz. Adjustable:rotary potentiometers to decrease or increase the width of the output pulse. 3 Modes:S-1 manual mode (Manual)/S-2-bit mode (Neutral)/S-3 automatic mode (Automatic) 1.This Digital Servo Tester is with high accuracy. 2.You can test control 4 servos at the same time and change the test modes as you need. 3.With rotary potentiometers, you can decrease or increase the width of the output pulse. colour:black Material:ABS size:40 x 75 x 25MM Package Contents: 3 x servo tester Notice: Carefully read the before any use, if you are a beginner, it/'s advisable to be assisted by an experienced adult.. Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.