An electronic apparatus for automatically detecting the length of network transmission lines. The electronic apparatus essentially comprises a detection device, an analog/digital (A/D) converter, a microprocessor, a frequency compensator and a transmission network line, such as an RJ-45 network transmission line. The electronic apparatus utilizes the detection device to detect a frequency response of the reference signal for generating detection signals and converts the detection signals into digital signal. Thereafter, the microprocessor outputs a control signal so that the frequency compensator, comprising resistors and capacitors, makes up for the video frequency according to the control signal. As a result, the optimum video frequency is generated to display a clear image on a monitor for the benefit of the operation.
A cable length detection apparatus is provided to detect the length of a cable having at least three pairs of wires for transmitting video signals. The cable length detection apparatus has a signal compressing circuit, a signal converting circuit and a length calculating circuit. The signal compressing circuit compresses an electrical signal into one pair of wires. The signal converting circuit converts the electrical signal transmitted by the pair of wires into a value. The length calculating circuit then calculates the length of the cable according to the value.
