NVC sensor head, one-key switching between two modes without contact. Detection along when the buzzer stops, the red light does not blink and the digital display screen has no signal strength is the breakpoint. Intelligently identify the zero fire line and quickly distinguish the zero fire line without touching. The zero and red light blink slowly, while the fire line and red light blink quickly. Support acousto-optic alarm, sensitivity adjustment, flashlight lighting and automatic shutdown function. Small size and easy to carry. Name:household measuring pen Power supply mode:2 AAA batteries(Not included batteries) Colour:Red & Black Material:Plastic Package Contents: 1 * Household electric pen 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.