The TR-6812U has universal input voltage of 24-240VAC & 12-125V DC on terminals 2 & 11 while the obsolete TR-68129 has 120V AC on pins 2 & 11 and 24V AC/DC on pins 7 & 11 (NOTE: some rewiring is required); the obsolete TR-68129 had 7 timing functions while the TR-6812U has 8 (the only function from the obsolete TR-68129 NOT available on the TR-6812U is On Delay/Off Delay).