According to one embodiment, a transmission system may include a plurality of signal processing apparatuses. The signal processing apparatus are connected in series. The signal processing apparatus includes a plurality of signal processors, and a switcher. The signal processors generate an output signal by performing signal processing of an input signal from an earlier-stage signal processing apparatus. The signal processors supply the output signal into which is included an abnormality signal if the input signal does not include the abnormality signal and also the output signal does not satisfy the criteria. The switcher receives a plurality of output signals output from the plurality of signal processors. The switcher supplies an output signal of the plurality of output signals.