From the Hardware Guide for Avaya Communication Manager, 555-245-207:
For the TN746B circuit pack:
Telephone Wire size (AWG) Maximum range(feet)
2500 type 24 (0.2 mm2/0.5 mm) 20,000 (6,096 m)
7100 series 24 (0.2 mm2/0.5 mm) 20,000 (6,096 m)
7101A 24 (0.2 mm2/0.5 mm) 15,200 (4,633 m)
7103A 24 (0.2 mm2/0.5 mm) 15,200 (4,633 m)
8100 series 24 (0.2 mm2/0.5 mm) 12,000 (3,657 m)
9100 series 24 (0.2 mm2/0.5 mm) 12,000 (3,657 m)
I currently support analog extensions up to 4200 feet away (straightline) from my CSi. Watch the gauge if you want to get these distances.