Spike Breaker

how is the spike breaker used in the pneumatic system?
does it regulate the solenoid?

The breaker/fuse in a spike relay protects the circuit from drawing too much current. Typically, pneumatic devices are a very low-demand application as far as electric current, but in the case of a short or similar malfunction, the breaker will shut the circuit down.

The spike itself is wired to the digital sidecar, and used to turn a solenoid on or off, if you do not have any ports available in the pneumatics breakout.

If you are using Labview, take a look at the Compressor VI in the examples. It shows you how to wire AND program the pneumatic system.

Mechanic,
A spike is needed to turn the compressor on and off. This is used with the compressor VI in Labview by reading the pressure switch and turning the Spike on. Spikes can also be used to control pneumatic solenoids but the solenoid module for the Crio is easier to implement from a wiring standpoint.
As a reminder, if you use the Spike for controlling a compressor, you should replace the 20 amp fuse in that Spike with a 20 amp circuit breaker.