The CX110+ is equipped with a built-in DOCSIS cable modem, which discovers the upstream frequencies by listening on the downstream channel for Upstream Channel Descriptor (UCD) packets. Once a special message called a map is detected, the cable modem begins to transmit upstream data starting at its lowest power level, incrementing in 3dB steps until the CMTS acknowledges the request.
Once detected, the CMTS analyzes the power, frequency and timing of the range request and send the cable modem a response which provides instructions for the modem to adjust its transmit power, frequency and timing to operate properly on the network. The upranging check functionality is very useful for technicians who are only concerned with the RF alignment and synch process when installing cable modems.