The Global Positioning System (GPS) signal contains several components, including timing codes and navigation data. Understanding which specific component is universally accessible by all types of receivers is key to determining its function.

Coarse-Acquisition Code Accessibility

The Coarse-Acquisition (C/A) code is a pseudo-random noise (PRN) sequence broadcast by GPS satellites on the primary L1 frequency (mathematical notation: $1575.42$ MHz).

• This C/A code is specifically designed for civilian and commercial use.
• Crucially, the C/A code is unencrypted and publicly available.
• Its non-proprietary nature allows all types of GPS receivers, regardless of manufacturer or specific model, to synchronize with the satellite signal and acquire positioning data.

Other Signal Components' Limitations

Alternative signal components are not universally accessible:

• Precision Code (P-code): This code is generally encrypted (forming the P(Y)-code) and reserved primarily for military applications, making it inaccessible to standard civilian receivers.
• Link frequencies: Specific frequencies like 'Link-1' or 'Link-2C' typically relate to specialized communication systems, satellite-based augmentation systems (SBAS), or military data links, rather than the core signal deciphered by every basic GPS receiver.

Therefore, the Coarse-Acquisition code is the essential component of the GPS signal that gets deciphered by all types of GPS receivers.