Level measuring system for data transmission lines - measures signal frequency from transmission end to operate frequency generator for return signals

摘要

The level measuring system for data transmission lines (NL1,2) uses a level transmitting device (PSM) at one end (MST) of the lines and a frequency measuring device (FMG) at the remote end (GST). This first measures the frequency of the signal (U1G) from the level transmitter. This is then used to operate a frequency generator (FPG) at the remote end which gives a signal (U2G) of constant level and transmits it through the return line (NL2). This has a frequency of a fixed predetermined ratio to the signal (U1G) received from the level transmitter. The frequency of the signal from the level transmitting device is wobbulated. The transmitted measuring signal (U2G) from the remote end (GST) is at the same level for all measuring frequencies. For frequency measurement, test measurement of the signal (U1G) received at the remote end, monitored for a periodic time, for which a backwards and forwards counter can be used.