Yamaha C-70 preamp - What is "Direct Phono"?

Hi - I just picked one of these up at a Goodwill and it seems to have a pretty nice, complete phono section with various cartridge options, etc. But there are 2 inputs for "Direct Phono" on the rear panel (1 for MM, 1 for MC). Does anyone out there know what these are for/do?

Cheers, Chip