| 1 | SIGX | Signal Gasoline Co. | 7/1932 | | NAKINA |
| 2 | SIGX | Southern Indiana Gas and Electric Co. | added 4/1979; 1/1980-7/2000; eliminated 7/2002; 7/2005 (not listed) | | NAKINA |
| 3 | SIGX | Southern Indiana Gas and Electric Co. | added 4/79; 1/80-7/2000 | | NRHS |
| 4 | SIGX | *SIGNAL GASOLINE CO. | | | PWRC |
| 5 | SIGX | +SOUTHERN INDIANA GAS & ELECTRIC CO. | | | PWRC |
| 6 | SIGX | Southern Indiana Gas and Electric | | | RSRV |
| 7 | SIGX | SOUTHERN INDIANA GAS & ELECTRIC CO. | | | SCAC4 |
