Abstract: A device for determining speeds of a digital signal in a serial transmission line. The device comprises a first and second counter and a logic circuit. The first counter is adapted to count the duration of a first pulse in a first byte of the digital signal in the transmission line. The second counter is adapted to count the duration of a second pulse in the first byte. The logic circuit is coupled to the first and second counters. The logic circuit is adapted to compare the smallest duration of the first and second pulses with a plurality of pulse duration's of known baud rates to determine the baud rate of the digital signal in the transmission line.