This wiki is about 0.16, the current stable version of Factorio.
Information about 0.17, the current experimental version of Factorio, can be found on wiki.factorio.com.
Decider combinator
Decider combinator 
Recipe 

+ + →  
Total raw 

+ + 
Recipe 

+ + →  
Total raw 

+ + 
Map color 

Health 
150 
Stack size 
50 
Energy consumption 
2 kw (electric) 
Calculations per 60 UPS 
60 
Prototype type 
decidercombinator 
Internal name 
decidercombinator 
Required technologies 

Produced by 

The Decider combinator is part of the circuit network and one of three types of combinators available in the game (with the other two being the constant combinator and arithmetic combinator). It is used to make comparisons of signals on the network. Signals can be compared using "is greater than" (>), "is less than" (<), "greater than or equal to" (>=), "less than or equal to" (<=), "is equal to" (=) and "is not equal to" (!=). Input contacts are to the left in the above picture, outputs on the right.
Function
The internal logic process has three steps:
 Values for each individual input signal(s) (items of the same name) on the red and green wires are summed within the combinator.
 The decider combinator GUI specifies a "first" input signal, a comparison (>, <, =, >=, <=, !=), and a "second" input signal or constant.
 If the comparison returns true, the output is a new signal with a value of 1, or copying an input signal to the ouput.
Further notes:
 Using the Everything output with input > output will pass all nonzero input values to the output as long as the condition is true. Using the Everything output with "1" will output 1 ONLY for all nonzero inputs.
 The Each input will reapply the comparison for each input signal individually, and will pass the selected output for each input that passes the conditional.
 The Everything input functions as a logical AND, and will return true only if ALL nonzero inputs pass the conditional.
 The Anything input functions as a logical OR, and will return true if ANY nonzero input passes the conditional.
 When "Input Count" is selected the "Parameters" don't affect the value of the output, only the summed input signals do.
The decider combinator can handle logic signals.
With both the arithmetic and decider combinator, there is one tick (60th of a second) of latency before the output signal is ready to be used as an input into a circuit network.
History
 0.15.0:
 Added additional operators to the Decider Combinator and Circuit Conditions.
 0.13.0:
 Connected wires are highlighted when hovering over a combinator connected to the circuit network.
 Combinators show input and output in alt mode.
 More virtual signals for combinators.
 Constant combinator can be rotated.
 Decider combinator "input count" option makes the combinator copy the count of the specified output signal from the input signals, instead of copying the count from the condition.
 New combinator graphics.
 0.12.5:
 Combinators now emit light.
 0.12.2:
 Combinators no longer turn off when no wires are connected.
 0.12.0:
 Introduced
See Also
 Arithmetic combinator
 Constant combinator
 Combinator tutorial < Description of Combinator Logic Gates
 Circuit network
 Circuit network cookbook