Sunrise sunset - a low voltage photocell intended for LED lighting.  

The sunrise sunset controls and varies LED light intensity via photocell. At sunset your lights slowly turn on and at sunrise they gradually turn off, optimizing system efficiency. Install in a place that is exposed to light, hookup is easy; wires inline between your power source and lighting load. Think of the sunrise sunset as a self-calibrating timer that is controlled by light. 

Dimensions: 

L: 4.25 W: 2.3 H: 2.80 inches unextended, 6 inches extended
Mounting: 2, D: ~.375 inch mounting holes

Electrical:

Voltage option: 12vdc or 24vdc
Hookup input: Red=positive+ Black=negative-
Hookup output: Yellow=positive+ Green=negative-
Current option a: capable of powering up to a .500mA or 6 watts
Current option b: capable of powering up to a 1A or 12 watts

Code:

Model: sunrise sunset (ss)
Current option: (a) for .500mA option or (b) for 1A option
Voltage option: 12 or 24vdc
Ordering example: ss-a-12vdc