One matrix board aggregate accommodating two matrix boards is made one unit of a switch. Three of the matrix board aggregates are vertically located, groups of such three vertically-located matrix board aggregates are laterally located and robots are provided between the matrix board aggregates. By providing a number of robots, the switch operation speeds up. The robots are controlled by a control circuit/power supply RMC/POW. I/O cables for connecting an MDF apparatus to an exchange or to lines are provided at the back. In a three-stage switching configuration, by devising the location of primary, secondary and tertiary switches, interconnection between matrix board aggregates can be made using BWBs made of a printed wiring board.