PURPOSE: To make the operation of a transmitter complete by sending a rescue signal while stopping a ship if a person falls down from the ship in sailing and not sending the rescue signal when the person can swim and return to the ship when the ship is at anchor so as to decrease the number of times of signal transmission.

CONSTITUTION: A slave set 1 of a rescue signal transmitter is carried by a passenger, a transmitted radio wave from the slave set 1 is received by a reception section 4 and inputted to an I/O section 31 connected to a CPU 28. The reception section 4 demodulates an input signal, the decrease in the input signal is detected by a signal detection means to start the clock operation of a timer means such as a reset switch 14 or the like. An alarm is displayed by an alarm lamp 32 at the same time or by a prescribed time after the detection signal, and the propelling torque of a ship is stopped by a stop drive section 22 after a prescribed time from the alarming. If a person falls down from the ship during the sailing, the rescue signal is oscillated and when the person can swim and return to the ship, no rescue signal is transmitted so as to decrease the number of times of signal transmission and to ensure the transmission.