The original MMR elevator door sensor switch model SB-51CR. There are two alternative methods: 1. Replacing with a photoelectric switch sensor:BEN10M-TFR1, BEN10M-TFR2 Power Supply: 24-240VAC / 24-240VDC Technical Specifications: Detection Object: Opaque objects, minimum diameter of 16mm Light Source: Infrared LED (850nm) Response Time: Maximum 20ms Power Consumption: Emitter max. 4VA Detection Distance: 10 meters … Continue reading The Alternative Method for The MMR Elevator Door Sensor Switch SB-51CR