From: Dan.Thorson@seagate.com
From what I recall there is no guarentee that the Qwest tarrif for NB3 is actually a straight-through copper pair [section 7.3.1.B.2.a.(4)]... note the restriction of signaling frequency.... see the Terms & Conditions in section 7.3.1.B.2.a.(2).
By requesting a circuit that offers 60Hz and/or DC signalling that pretty much requires them to use Copper, if they have it available. The only way to know if they have it available is to order the circuit. After a few days the order will hit their design department which will look at the order and determine if facilities exist to provison the circuit. Some newer office towers and subdivisons/developments may be fed with fiber using Digital Loop Carrier(DLC/SLC) equipment in a CEV hut. While there is still a copper loop to each home or business from the CEV/Hut, the loop ends at the SLC and the voice is converted to PCM over fiber to extend to the C.O. Our Telco uses a slightly different wording in their Tariff for this lack of DC continuity disclaimer...: "The provisioning of metallic or DC continuity applied until 1993 12 31. Thereafter, the provisioning of metallic or DC continuity is provided only where metallic facilities currently exist, following normal provisioning practices. Where capacity is exhausted, or where appropriate facilities do not exist, the Company will evaluate all requests and only provide end-to-end metallic facilities at the customer's expense based on the cost incurred by the Company." The largest concern is usually the length of the circuit because how they route the circuit is not always intuitive and the cable may take a circuitous route between your two locations. Usually they can estimate the loop length when the do the design. The limitation on frequency/pulses is largely administrative verbiage. I highly doubt they will install a filter on the circuit to prevent higher speed. (Although it is possible) At one time I think the different speed circuits where priced differently. I suppose a few decades ago the differnce between 30 bits per second and 75 bits per second was considered a large amount of difference. ;-) -Randy