TRIODE
| Date | Clue |
|---|---|
| 2021-09-05 | Vacuum tube type |
| 2019-11-24 | Amplifier of radio signals |
| 2018-10-14 | Old vacuum tube |
| 2018-08-05 | Certain vacuum tube |
| 2013-07-28 | Old TV component |
| 2011-08-04 | Old vacuum tube |
| 2007-03-11 | Old TV part |
| 2006-07-17 | Certain vacuum tube |
| 2005-01-02 | Vacuum tube |
| 2004-12-16 | Old TV part |
| 2003-06-13 | Television tube |
| 2001-08-02 | Certain electron tube |
| 1999-04-10 | Old radio tube |
| 1999-04-07 | Vacuum tube with three elements |
| 1995-08-11 | Certain tube |
| 1995-03-04 | Vacuum-tube type |
| 1995-02-05 | Vacuum tube type |
| 1994-02-28 | Vacuum tube |