PURPOSE: To improve the workability for address setting and to reduce setting mistake by using an operation display light of a slave set so as to read address data from a memory of the slave set, sending the data by light, using a light receiving section provided to a master set to receive the light and registering the address data to a memory.

CONSTITUTION: A slave set 12 is provided with a drive control means 24A reading address data registered in advance in a memory 35 to control drive of lighting of an operation display light 18, and a master set 14 is provided with a light receiving means 100 receiving a light emitted from the operation display light 18 and with a write control means 64A controlling write of the address data in a memory 102 based on the output from the light receiving means 100. The address data registered in advance in the memory 35 are read by the slave set 12 to drive light emission of the operation display light 18 and the master set 14 receives the emitted light from the operation display light 18 and writes address data in the memory 102, then it is not required to replace the address data with a binary number at setting of the address data.