Closed training. It is normal for closed training without a mobile phone. There are many kinds of closed training. The most common is the group building of the company. Find a place that can provide accommodation and catering, expand the theory and ask all mobile phones to be handed in. Half a month at most. At least two or three days. One is to train the company's latest business theory. Exchange their experiences. The second is through expansion. Increase the cohesion and centripetal force of the company. Therefore, closed training is not allowed to train mobile phones from morning till night.