A control character is sent at the beginning as well as at the end of each block in the synchronous-transmission in order to.

• a
  Synchronize the clock of transmitter and receiver.
• b
  Supply information needed to separate the incoming bits into individual character
• c
  Detect the error in transmission and received system.
• d
  Both (1) and (3)

Supply information needed to separate the incoming bits into individual character