Abstract: For monitoring and controlling the traffic in a transmission network of a multiplex hierarchy stage comprising circuit switching devices connected via digital signal sections, all digital signals to be fed in are supplied at their source with an identification character for a desired digital signal connection. The identification character is communicated to all involved circuit switching devices so that the same can be tracked along the digital signal connection and the circuit switching devices are correspondingly controlled. Idle digital signal sections can be maintained active with an alternate signal which contains an alternate signal identification character. Given a disturbance of a digital signal section, an alternate circuit can be switched.