An electrically insulating mechanical joint checker for mechanical joints connecting rails of following track segments of a railway line, each track segment forming part of a track circuit. The track segment includes electric signal transmitting units and receiving units for transmitting and receiving train presence detection signals within the track segment and/or relating communication signals between the train and the track segment. The train presence detection signals and communication signals include a further joint detection signal, generated and transmitted by the transmitting units and received by the receiving units belonging to the same track segment, the joint detection signal relating to the track segment being different at least in respect to the one relating to the adjacent track segments. A method to detect a failure or breakage of a mechanical joint inside a track segment is also disclosed.