Telephone tapping in the countries of the Eastern Bloc was a widespread method of the mass surveillance of the population by the secret police.
Telephone tapping in the Eastern Bloc Wikipedia
In some countries, this was open and legal. During martial law in Poland, official censorship was introduced, including open phone tapping. In fact, the Polish secret police did not have resources to monitor all conversations, despite the introduction of the new censorship division.
In Romania, telephone tapping was conducted by the General Directorate for Technical Operations of the Securitate. Created with Soviet assistance in 1954, the outfit monitored all voice and electronic communications in and out of Romania. They bugged telephones and intercepted all telegraphs and telex messages, as well as placing microphones in both public and private buildings.
The 2007 film The Lives of Others concerns a Stasi man who is telephone-tapping a suspected dissident writer.
The Polish comedy film Rozmowy kontrolowane (Monitored Conversations) capitalizes on this fact. The title alludes to the pre-recorded phrase "Rozmowa kontrolowana" ("The talk is being monitored") a person repeatedly heard during a phone conversation.