Fire Protection Systems In reference to aircraft fire-extinguishing systems, (1) during removal or installation, the terminals of discharge cartridges should be grounded or shorted. (2) before connecting cartridge terminals to the electrical system, the system should be checked with a voltmeter to see that no voltage exists at the terminal connections. Regarding the above statements, a. only No. 2 is true. b. both No. 1 and No. 2 are true. c. neither No. 1 nor No. 2 is true.