During the great liberation war there was no advanced communication system or technology like now. It took a lot of hard work to get a little communication and in the end it was doubtful to be successful. During the war of liberation, the fighters used to communicate mainly through radio signals. There were secret signals on a particular radio in a song or in a sentence of a news story so that others could not understand. An example of this is when the freedom fighters got a signal when the song "I heard as much as you did" sung by Pankaj Mallick on Akashvani Radio on 13th August. As a result, on 15 August, a naval team planted a mine in the Pak army port and sank the ship in a violent explosion. In this way a small signal was given with great difficulty.