PURPOSE: To check whether or not the system is in normal wiring condition in operation by having an observation instrument on board, a signal line, a posture detector, wherein a switch which opens or closes according to the posture of a grappling machine and a resistance are connected, and a cable catch detector, wherein a switch which opens or closes by the pressure at the time of grappling a submarine cable and a resistance are connected.

CONSTITUTION: A cable grappling machine signal system 60 is composed mainly of an onboard observation instrument 52, a signal line 54 which is incorporated in a towline a posture detector 62 which is mounted on a posture stabilizing plate 44 or a grappling element 42 and a cable grappling detector 64 which is mounted on grappling element 42. The cable grappling detector 64 is incorporated with a switch S2, which gets in ON condition when it grapples a cable, and a resistance R2 which is connected in series to this. In the posture detector 62, a switch S1, which gets in ON condition at normal posture and OFF condition at inverse posture, and a resistance R1, which is connected in series to this, are incorporated.