Installation of equipment usually presupposes a certain level of performance. Devices exist to ensure operation of transmission equipment at required service levels, however variation in service quality in transmission of signals occur due to the quality of transmission media, disturbance, available bandwidth and sensitivity of equipment.
Variation in line conditions places a larger onus on sensitivity of installed equipment. Rate Adaptive Digital Subscriber Line (RADSL) was developed in order to achieve variations in throughput and be sensitive to line conditions. It allows the flexibility to adapt to line conditions and adjust the bit rate at both ends to achieve optimum throughput in each line. Data transfer rates in both upstream and downstream directions can be seen changing with the change in line conditions. Speeds up to 768 kbps are offered by vendors offering RADSL services (Bates, 2000).