LOOPBACK TEST FOR DATA-TRANSMISSION CHANNELS

摘要

A data transmission path comprises a first and a second station, a first data transmission channel operative for synchronously transmitting data from the first to the second station in synchronism with a predetermined clocking schedule and at a respective first maximum data transmission rate, and a second data transmission channel for asynchronously transmitting data from the second to the first station at a respective second maximum data transmission rate, the first maximum data transmission rate being equal to a multiple p of the second maximum data transmission rate. A test waveform is applied to the first station for transmission to the second station along the first data transmission channel, the test waveform presenting a data transmission rate at least approximately equal to said first maximum data transmission rate. A test waveform, as received at the second station, is applied to a selector circuit whose output waveform is applied to the transmitting input of the second station for transmission back to the first station along the second channel. The selector circuit transmits to its output only every p-th one of the waveform elements applied to its input, relying on clock signals which the second station produces one per waveform element of the synchronously transmitted test waveform. The shortest waveformelement duration of the waveform produced at the output of the selector circuit at least approximately corresponds to said second data transmission rate.