Good job! One correction: early in the article you mention a "DEX;" I believe that should be a "DACS." DACS is "Digital Access Cross-Connect."
A DACS is an infrastructure switch for phone circuits. For example, a 3/1/0 DACS can accept a DS3, DS1 (T1), or DS0. It can take individual circuits (DS1 / DS0) from one DS3 and switch them into another DS3.
DACS is the technology that allows individual T1s (or DS0s) from many locations and present them to the home company office as a single T1 or DS3 (or fractionals).
DACS is a big cost-saver for the transport folks (carriers / telcos, etc) by virtue of a feature called "Groom & Fill." If you have a group of partially-used circuits (frac T1/DS1, frac DS3), and they're all going to roughly the same place, the used channels can be collected (groomed) and used to make a single, full, "big pipe" (DS3 or higher, depending on the system).
It also allows the Telco / carrier / transport / "long lines" folks to switch the circuits remotely. They use to have to send out a Hole & Pole person to physically switch the wires ("the pairs") from one bundle to another. That's why it used to take months to get a T1 installed; the circuit had to be manually mapped from one end to the other. Nowadays, most of the delay is administrative and regulatory; the circuits can be mapped from a remote terminal in a few minutes (and tested in a few more - (except extended BERT tests take hours).
The other thing is the "test jacks;" they're called "bantam jacks." They look like small banana jacks ...
Good Job!
Scott
