To form a plurality of communication paths and transmit and receive vital data between medical instruments.

Collective corridor lamps 11a, 11b, 11c and 11d which are installed in a plurality of respective sickrooms A, B, C and D along with bed slave apparatuses 1a to 4a, 1b to 4d, 1c to 4c and 1d to 4d are connected by one pair of main feeders L1 to a control device 13 to which a plurality of nurse call master apparatuses 12a, 12b, 12c and 12d to be installed in a nurse station are connected, and frequency multiplexing is effected by means of carrier waves using the one pair of feeders; the carrier waves are time divided and separated into a plurality of slots and communication paths are allocated to the slots, whereby simultaneous two-way communication between the bed slave apparatuses in the same or different sickrooms and the nurse call master apparatuses in the nurse station is made possible. Also, using some of the slots, vital data associated with monitoring of blood pressure, pulse rate, administration of medicine and the like can be transmitted and received between medical instrument terminals 10a, 10b, 10c and 10d and a medical instrument main body 14.