Abstract: For checking transmission and monitoring devices of digital transmission links, it is known to overlay code errors into the digital signals to be transmitted. In accordance with the invention, the code errors are overlaid such that given the prerequisite of a redundant transmission code, no falsification of the informational content of the digital signals arises. In accordance with the invention, this is undertaken in that the mode condition in the connected mode memory is modified and output to the mode input of the code conversion logic as a new sequential mode.

Abstract: A remote fed intermediate regenerator for use in transmission lines for digital signals having no direct current component has for each transmission direction a series circuit including a distortion corrector a regenerator circuit and a transmitting amplifier. For isolating the signal path and the remote feed path each intermediate regenerator is preceded and followed by remote feed dividing filters and each intermediate regenerator contains a high power Zener diode bridging the remote feed path of the regenerator and the distortion correcter and regenerator circuit each contain low power Zener diodes for stabilizing the operating voltages thereof. A transmitting amplifier for the intermediate regenerator has dynamic current characteristics and operates to stabilize the voltage without the necessity of a Zener diode and accordingly does not require a high-value input impedance thereby avoiding a significant power loss.

Abstract: A pulse code modulation regenerator includes an input transformer which is connected to an amplitude decision device with its output connected to a phase discriminator and to a time decision means, and which has a pulse generator connected through a low pass filter to the phase discriminator. The output of the pulse generator is also connected to the time decision device.