TDS/Conf is a dual purpose card:
TDS: Tone and Digit Switch. It's in charge of sending different kind of tones (dial tone, busy tone, ring back tone, etc)
Conf: Conference, you use it every time you make a conference (3-way or 6-way). It can also broadcast music and provide several features.
Every service loop can be used for 30 parties
You should have at least 1 TDS/conf in every NET shelf.
You can check in LD 2 -INVS 2: if you have FTMs you may need TDS/conf cards.
Regards,
JGutierrez