According to Baidu Encyclopedia, soldiers standing guard in Tiananmen Square are not allowed to talk to their parents while standing guard. The army has strict regulations, even if the guard is changed, the soldiers should keep a straight posture and not relax talking to their parents until the guard is changed.

Soldiers are not allowed to leave their posts or do things unrelated to their posts when they are on guard. People will check them around, and the duty of soldiers on guard is to maintain the order at the scene and the image of a soldier.