GPS satellites transmit several different carrier frequencies and apply different modulation codes to those carriers. The NetRS is capable of tracking several kinds of codes. On the L1 frequency (~1575 MHz) the C/A-code is always tracked. On the L2 frequency (~1255MHz), multiple codes may be available. On older satellites, the encrypted Y-code is usually all that is available. This signal was designed for military users and cannot be tracked directly without using militarized equipment. The NetRS normally uses a Trimble-proprietary cross-correlation method to track these Y-code signals.

Newer GPS satellites may modulate the L2 frequency with a second code designed for civilian use. This is the L2 Civil Signal, often refered to as L2C. The NetRS is able to track L2C signals when they are available. This capability can be enabled or disabled via the L2C Tracking Control page.

• Use the Enabled radio button to turn L2C tracking on. When enabled, the NetRS will attempt to track L2C codes. If an L2C signal is found on a satellite, then the L2 measurements for that satellite will be based on L2C. If the L2C code is not found, the NetRS will fall back to measuring the Y-code using cross correlation.
  
  
• Use the Disabled radio button to turn L2C tracking off. When disabled, the NetRS receiver will not attempt to track the L2C signals, and will only produce L2 results based on Y-code, tracked using cross correlation techniques.