I have here a software able do decode a quadrature of signals, which is exacly the protocol used by satelite GPS positions information, that is depending always on 4 satelites transmission togehter, to get precise positions, because of the amplification receivers noise. In this software meanning data aquisition processor port decoder command; on this attack I'm pretending to duplicate the signal, and confuse the call, so the satelite will think my signal is the true one.

Quadrature encoding and decoding

The purpose of the QDECODE command is to monitor and decode pulse sequences that arrive on a pair of digital lines on the Data Acquisition Processor digital input port. These particular digital logic signals are produced by a quadrature encoder attached to a device that can rotate forward or backward. The QDECODE command must determine the current angular position by monitoring the digital pulses. You can do this monitoring using special hardware devices, with excellent efficiency at high speeds. When you don't have the high speeds, however, this command might allow you to dispense with that extra hardware. 

http://www.mstarlabs.com/apeng/techniques/qdec.html