Never heard of it and I'm in the phone business. Sounds like maybe someone trying to describe ISDN-BRI or DSL. Either way, it just uses standard twisted pair wiring, CAT3 is more than sufficient for these services.
Sounds like a "pair gain" term. Read some stuff about it here: http://en.wikipedia.org/wiki/Pair_gain They don't mention a "DAML" which I've run across. I'd guess it's a Digital multiplexor. Basically you get one pair from the CO, and it gives you 2 POTS lines. Careful, the pair from the CO has 100+ VDC on it!
An "overline" is telco terminology for an additional phone number on the same line - as in when a business has 2 lines but only one receptionist. Both numbers ring on the same phone.
