Referring to training a conveyor belt, the belt should ride on all idlers without skewing, accomplished by proper structural alignment and by adjusting troughing and return idlers.
To operate effectively, echo cancellers need to monitor the echo received from a remote site within the local conference room and generate a correction signal to cancel the echo. This alignment procedure is termed `training'. This process considers not only echo from the remote site but also the acoustic characteristics of the local conference room. If the local room has poor acoustics, e.g. a high ambient noise level or very long term echo, then the echo canceller may not be able to achieve a satisfactory alignment. The local site will then introduce annoying echo into any conference in which it participates.
When using a conventional analog modem, you generally hear noise as the connection is established. DSL modems, similar to your analog modem, will negotiate (without the noise) with the phone company equipment to establish a set of rules, by which both will communicate. This is called training. Factors such as speed and rates are established during training. Training needs to happen anytime you lose connection with the telephone company's equipment, such as when you power your PC off and back on again. Training is a separate process from logging into your ISP; however, they are often viewed as the same, since they happen consecutively. You might be able to train, without being able to log into your ISP. You will never be able to log into your ISP without first being trained.