A data repeating device that can maintain the data integrity in error-prone circumstances. A network system involves a data communications device and a data repeating device interconnected via a transmission line. The data repeating device has an error detector for detecting a failure, based on errors found in received frames. Upon detection, a frame generator transmits an error correction enable frame to the data communications device, thereby requesting the use of error correction coding. Inside the data communications device, a correction activation flag is set in response to the received error correction enable frame, which indicates that error correction coding is to be applied. The active state of this flag permits an error correction coder to add an error correction code to each outgoing frame, thereby creating error correction coded frames for transmission over the transmission line.