SPECIAL ORDER ITEM. Review Returns Policy before purchase. The Photocell for Remote Transformer Installations is compatible with all Professional Series, Contractor Series and Plus Series transformers. Ideal for when you need to install a transformer inside, the 10 ft cord reaches outdoors to sunlight. Used for automating on and off sequencing, it features a dusk to dawn lighting sensor that turns the lights on when it gets dark outside and turns them off when it gets light.