The A. C. switches supply power as follows:
No. 8. When up, supplies the operating boards, one pole to boards, the other to earth through an independent lead; when down, it does the same, but the side grounded is grounded through a choke coil.
No. 9. When up, energizes the A. C. busses from motor-generator No. 1; when down, the A. C. busses from motor-generator No. 2.
No. 10 is spare.
No. 11. When up, supplies power to the primary of the testing transformer; when down, it is spare.
No. 12. When up, supplies power from the secondary of the testing transformer to the test fuses.
Voltmeter receptacles and plugs, all of which are properly marked, are provided for obtaining the reading of the A. C. and D. C. voltages. The D. C. receptacles are on the right and the A. C. on the left. The first receptacle of each set is spare to hold the plugs when the latter are not in use.
With the D. C. plug:
In the second receptacle, the voltage of the casemate generator is indicated.
In the third receptacle, voltage of external D. C. power.