Navigational control posts were stations within a particular area of space which guided and managed vessels through that area.
The Cardassians maintained at least twenty-four navigational posts within their territory. They would use their sensors to determine the types of vessels within their territory and decide if they were a threat or not. They were also able to dispatch repair ships to assist disabled vessels.
While these posts were able to scan and communicate within a wide area, the quality of communications degraded with distance from the post. At the extreme edge of scanner range, only audio contact was possible.
Kira Nerys and Miles O'Brien used this to their advantage in 2370 when they infiltrated Cardassian space in a runabout disguised as the Lissepian transport Martuk. Cardassian Navigational Control Post 24 detected their runabout as the Lissepian transport, but the modifications showed up as an engine malfunction that got the attention of the Post. Kira was able to convince the commanding officer that they did not require assistance, and the runabout was able to continue on its mission to rescue Li Nalas from Cardassia IV. (DS9: "The Homecoming")