1. Photoelectric Sensors: Photoelectric sensors, also referred to as optical sensors, are the commonest variety of garage door sensor. These sensors include two units: a transmitter and a receiver. The transmitter emits an invisible beam of sunshine, even though the receiver detects the presence or interruption of the beam. https://mariobytmf.tribunablog.com/new-step-by-step-map-for-lubrication-services-for-garage-doors-41368923