Check out L14G1 pdf, L14G1 Description, L14G1 Datasheet, L14G1 view ::: ALLDATASHEET :::
If I remember my transistor theory correctly, a phototransistor only requires two legs -- a collector and an emitter, because the light that enters the phototransistor's lens serves as the base that switches the output signal.
I believe (someone correct me if I'm wrong) that when the base is provided on a phototransistor than the base can be used to switch the transistor in the dark...