Find passive constructions in the text. What tense (or tenses) are they referred to? Find passive constructions in the text. What tense (or tenses) are they referred to? Text: General. All electrical work should be performed by qualified and experienced workers. Equipment shall be locked or secured to prevent starting by unauthorized persons. Live parts of apparatus and wiring shall be effectively guarded to protect all workers or objects from coming into contact. All equipment and wiring shall be checked daily by the operator before starting work. All electrical circuits shall be grounded. Warning signs or posters, such as DANGER, NO ENTRY, shall be displayed at dangerous places, such as substations, switch boxes, and overhead or underground cables. Transformer Bank. Transformer banks or high voltage equipment shall be barricaded with a fence. The entrance shall be locked. For transformer banks, warning signs of DANGER, NO ENTRY and NO WATER SPRAYING shall be posted. Posters shall show the name of the supervisor or maintenance engineer. Voltage and capacity also be displayed. Circuit Breakers. Circuit breakers shall be provided for all electrical equipment, such as conveyors, winches, pumps, grinders and similar equipment, to prevent workers from being injured by electric shock. Automatic leakage breakers installed in switch boxes are preferable. Switch Boxes. Temporary switch boxes shall be constructed of metal with a water-proof roof and door which can be locked. Switch boxes shall be installed adjacent to the work area at a height of 80 centimeters or more from the ground or working floor. An ample number of switch boxes shall be provided with adequate capacity. Switches and fuses shall be of proper capacity for the circuit protected. Overloading beyond the rated capacity shall be prohibited. The name of the person responsible for inspection and maintenance of the switch box shall be marked on every switch box. Name or number of equipment to be served by each switch shall be tagged on each switch. Switch boxes shall be grounded with vinyl-insulated copper wire. Multiple connection of cables from one switch shall be prohibited. When inspecting or repairing, switches shall be cut out and the switch box locked. Wiring. Wiring shall be cab-tyre cable having a dielectric strength of not less than the rated voltage of 600 volts. Cable having ample capacity to the load shall be used. All cables shall be installed away from any steel materials, such as wire rope, steel-frame scaffolds, etc. Grounding. To prevent short circuit or electric shocks, special precautions, such as grounding, shall be taken for wiring work where metal scaffolds or steel structures are erected. Grounding shall be ensured by connecting the wire to an earth rob buried firmly in the ground. Brass or steel bolts and nuts shall be used for grounding terminals of all electrical equipment.