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Blu-ray (Otis uses 3 wires)

Blu-ray (other brands use 4 wires)

White light (3 lines for Otis)

White light (other brands use 4 wires)

Red light (Otis uses 3 wires)

Red light (other brands use 4 wires)

A311 red light

The button is divided into blue light, white light, and red light, but the color of the light is different. For Otis, please buy 3-wire (Otis has no red light), other elevator brands please buy 4-wire, 3-wire and 4-wire cannot be used in common. 3-wire and 4-wire refer to internal wiring, not visible from the outside. There are 4 pins.