The mechanism, they use "caesium oscillator" which calculate "a second as the duration of 9,192,631,770 cycles of radiation corresponding to the transition between two energy levels of the ground state of the caesium-133 atom".
In layman's term, it is a very precise clock!!
"Time is precious, and accurate timekeeping is vital to everyday Malaysian life, as well as to international and high technology activities. On August 5, 1992, the Malaysian Cabinet appointed the National Metrology Laboratory to be the national timekeeper.
The national atomic time scale is established and maintained using five Caesium atomic clocks, two of which are high performance and three of which are standard performance. These five atomic clocks are compared to one another in order to detect any abnormality or instability. One of the clocks is designated as the reference clock. By virtue of its participation in the International Bureau of Weights and Measures GPS common view time transfer, the Malaysian atomic timescale is traceable to the International Atomic Timescale."