A wedge member for securing an electrical conductor box within a hollow concrete block which is to be incorporated in a concrete block wall. The wedge member includes an elongated member dimensioned for a force fit within a hole within the concrete block.

A junction box is configured to be arranged between a DC power source and a load. The junction box includes a first mechanical relay configured to be connected to a positive terminal of the DC power source, a second mechanical relay configured to be connected to a negative terminal of the DC power source, a semiconductor relay connected in series to at least one of the first mechanical relay and the second mechanical relay, and a controller that controls driving of the first mechanical relay, the second mechanical relay and the semiconductor relay respectively. When an abnormal state occurs, the controller controls the first and second mechanical relays to turn the first and second mechanical relays off after controlling the semiconductor relay to turn the semiconductor relay off.