On May 19, 2025, at 16:50 Moscow time, a few minutes before the start of a telephone conversation between Russian President Vladimir Putin and US President Donald Trump, a Russian shortwave radio station known as "The Buzzer" (UVB-76 or The Buzzer) transmitted an unusual message: "NZhTI 89905 BLEFOPUF 4097 5573."

The message sparked a wave of speculation among radio enthusiasts and analysts given its timing with a key diplomatic event.

Operating on 76 kHz, UVB-4625 is known for its monotonous buzzing signal that is broadcast 24 hours a day, with occasional voice messages in Russian. The station, believed to be operated by the Russian military, has been broadcasting since the 1970s, and its purpose remains a mystery. Messages like today's typically include code words and numbers, which one theory is that they may be intended for military or intelligence purposes. Today's Monolith message consisted of the call sign NZhTI, the five-digit identifier 89905, the code word "BLEFOPOOF," and two four-digit numbers, 4097 and 5573.

The telephone conversation between Putin and Trump, which began at 17:00, was devoted to a possible ceasefire in Ukraine. According to White House press secretary Caroline Levitt, Trump expressed disappointment with the positions of both sides in the conflict, but sought a truce. Putin, in turn, declared his readiness for a temporary ceasefire on the condition of "irreversible guarantees," including the withdrawal of Ukrainian troops from the Kursk region. The coincidence of the "Buzzer" message with this event gave rise to hypotheses about its possible connection with military or diplomatic processes.