A control system includes a plurality of driving circuits coupled in series, which include a first driving circuit and a second driving circuit. The first driving circuit includes a first receiver, a first transmitter and a first flag signal selector. The first transmitter is coupled to the first receiver, and the first flag signal selector is coupled between the first receiver and the first transmitter. The second driving circuit, coupled to the first driving circuit, includes a second receiver, a second transmitter and a second flag signal selector. The second transmitter is coupled to the second receiver, and the second flag signal selector is coupled between the second receiver and the second transmitter.