The remaining switches, receptacles, and attachments are sufficiently well indicated in the figures. Switch No. 1 controls the lamps at the top of the board. When it is up, they are supplied from an external source of power. When it is down, they are supplied from the storage battery. The D. C. terminals are all carried to one terminal bar, the A. C. terminals to another. All terminals and all switches are labeled. Provision is made for energizing the D. C. busses: (_a_) From an external source of power: Close single circuit breaker and close switch No. 2 to the right—facing the board. (_b_) From the casemate generator: Close single circuit breaker and close switch No. 2 to the left—facing the board. (_c_) From the storage battery: With switch No. 2 open, close double circuit breaker. Feeder switches are plainly marked. The D. C. switches supply power as follows: No. 3. When up, supplies the operating boards (negative pole to boards, positive to earth); when down, it is spare. No. 4. When up, supplies motor-generator No. 1; when down, motor-generator No. 2. No. 5. When up, supplies the mine commander’s station. No. 6. When up, supplies casemate lamps; when down, it does the same, but the power is now drawn from an external source and not from the D. C. busses. No. 7. When up, grounds the positive bus and connects the negative bus through the protective lamp and mil-ammeter to the mil-ammeter lead. 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. In the fourth receptacle, voltage of storage battery. With the A. C. plug: In the second receptacle, voltage of A. C. power on the busses is indicated. In the third receptacle, voltage of external A. C. power, if the latter is supplied. In general, no external A. C. power should be led into the casemate, as the system would be unsafe, owing to the liability of a “cross.” The standard system is perfectly safe, as it is impossible for a mine to be fired when the motor-generators are idle.