2670 KHz is designated a ___________________ __________________ frequency, and use by other stations is restricted to communications with them.

2670 KHz is designated as a maritime rescue frequency, specifically allocated for distress communications and search and rescue operations. This frequency is crucial for ensuring safety at sea, as it allows mariners in distress to communicate effectively with rescue services and other vessels. The restriction of use to communications related to maritime rescue helps prevent interference and ensures that the channel remains clear for emergency signals, enabling prompt responses to emergencies at sea.

The other options do not accurately reflect the primary purpose and regulatory restrictions related to this frequency. For instance, naval operational frequencies would encompass broader military communications rather than being specifically dedicated to rescue operations. Additionally, ship-to-ship communication does occur on various other frequencies, but 2670 KHz is not designated uniquely for that purpose. Lastly, radiotelephone private communication suggests a form of usage that contradicts the open and emergency-oriented nature of the maritime rescue frequency.