The Data Test Unit, TPI 105, is a portable digital services tester. It supports DSO, DS1, 4 wire local loop, 4-wire Switched 56, T-1 and fractional T-1 services, and ISDN LT, Layer 1 testing.
The Data Test Unit has the capabilitiy of testing both the Primary and Secondary Channels, independently, at data rates of 2.4, 4.8, 9.6, 19.2, 38.4, 56, and 64 Kb/s.
TPI 105