PURPOSE: To prevent the unlocking operation with the illegal behavior by setting the discrimination time at the time of unlocking in response to the length of the code signal to be transmitted at the time of locking operation.

CONSTITUTION: A CPU 13 stores the transmitting time of the code signal, which is sent from a transmitter 1 at the time of locking operation, with a memory 14 and a counter 15, and the CPU 13 discriminates that the code signal is transmitted over the stored time or not at the time of unlocking operation. At the time of locking operation, locking is immediately performed with the first code signal, but the transmitting time at this stage is set as a time to be required for the confirmation at the time of unlocking operation, the whole of the code signal necessary for the unlocking becomes a long signal, which is hard to be copied by a learning remote control, and the unlocking operation with the unfair behavior can be surely prevented. The code signal transmitting time can be desirably set by changing the ON time of an operation switch 5.