The Revolution's six auxiliary outputs are open collector.  They can be interfaced to a PICAXE or PIC microcontroller using the circuit below.

The microcontroller and the Revolution receiver must share a common ground.  This can be accomplished by connecting the black wire from the auxiliary connector to the ground on the microcontroller. 

The input pin on the microcontroller must be pulled high with a 10K resistor.  The 1K resistor protects the input pin on the microcontroller and is recommended but not absolutely necessary.

When the auxiliary output from the Revolution is off the input pin on the microcontroller will be high.  When the output is on the pin will be low.

The example here uses a PICAXE 08M and input #3 (pin 4).