The format is derived directly from the design of the teletypewriter, which was designed this way because the electromechanical technology of its day was not precise enough[citation needed] for synchronous operation: thus the systems needed to be re-synchronized at the start of each character. Having been re-synchronized, the technology of the day was good enough to preserve bit-sync for the remainder of the character. The stop bits gave the system time to recover before the next start bit.