TAU photocells are designed for garage doors, security shutters and blinds. Operating range up to 20 meters. For systems with two pairs of photocells, in the case that AC power has 12-24 V AC can be used synchronization. The phases of the first pair must be linked back to the phases of the second pair. If not, avoid the installing of the two receivers on the same side. Best will instead be to switch the places of the receiver with the transmitter.