PURPOSE: To reduce improper connection or the like while many peripheral equipments are rationally simultaneously connected through a connecting connector, on condition that a number of main unit connectors, which must be provided in an equipment main unit, is suppressed to a minimum limit.

CONSTITUTION: A main unit connector 11 is protrusively provided to also provide a protrusive letter-shaped guide recessed part 13 in an equipment main unit 10. Relating to the main unit connector 11, branch connecting connectors 30, 30, 30,..., respectively mounted on a plurality of peripheral equipments 21 to 25, are fitted to be connected in series, in a condition that connecting protrusive parts 33 of the connectors 30 are successively fitted to the guide recessed part 13, by alternately arranging a plug part 31 and socket part 32 of these connectors 30.