Historical clue formulations

• Trigram on rotary phones — 2014-01-29
• Old phone trio — 2013-11-16
• Phone pad letters — 2013-04-14
• 7, on a phone — 2006-03-24
• Telephone trio — 2002-11-27
• 7, on a phone — 2000-08-28
• Couples: Abbr. — 1999-08-10
• Duos: Abbr. — 1997-05-01
• 7 on a dial — 1996-02-25