To reinforce a system function, and to improve reliability and a feeling of safety by making a plurality of remotely installed alarm systems cooperate with each other by using the network of a power smart grid system for performing the automatic meter-reading or control of the electric power consumption of a client.

Two alarm systems having a plurality of smoke alarms 10-11 to 10-22 which issue alarms in cooperation with each other when detecting a fire, are installed in a plurality of houses 12-1 and 12-2, and made to cooperate via a power smart grid system having power smart meters 14-1 and 14-2 connected to the Internet 22. When a fire is detected by the alarm 10-11 of the house 12-1, a fire cooperation interlock signal is transmitted via the power smart meter 14-1, a power company server 24, and the power smart meter 14-2 to alarms 10-21 and 12-22 in another house 24-2, thus the fire alarm of the other system is output.