how-to block ads
Training the line means to negotiate the best possible speed on the line. Sometimes, line noise can interfere with normal DSL line traffic, so, the modem must negotiate the best possible speed despite the noise.
With the noise, the best speed can't be offered, so, it throttles the speed back through a negotiation sequence so that you can get the best speed and connection stablility despite the noise.
Also read About DSL for lots more information