listening post

noun3

1. •
   A position established for the purpose of detecting the enemy's movements by means of listening.
2. •
   A facility established to monitor radio and microwave signals and analyse their content to secure information and intelligence for use by the security and diplomatic community and others.
3. •
   Any location frequented by a journalist in search of stories or gossip.

   • The British crown colony of Hong Kong is the West's primary listening post for information on Red China, which does not grant entry visas to many foreigners. — 1963