An apparatus for remotely monitoring a plurality of devices on a display device, the devices being directly or indirectly connected to a network, the apparatus comprising a display control section adapted to display a tree diagram of the devices, wherein said apparatus further comprises: a selecting section adapted to select one of a plurality of grouping systems of the devices, each of the devices allocated to at least a first and second grouping system, wherein the display control section is adapted to select one of the first grouping system and the second grouping system so as to display the tree diagram of the devices corresponding to only the selected one of the first grouping system and the second grouping system, characterized in that said devices are amplifiers (6a, 6b, 7a, 7b) provided to process audio signals, and have at least a first group code corresponding to the first grouping system and second group code corresponding to the second grouping system; and in that said apparatus further comprises: a collecting section adapted to collect the group code corresponding to the selected grouping system, selected by the display control section from each of the amplifiers (6a, 6b, 7a, 7b) through the network; wherein the display control section is adapted to display a tree diagram of the amplifiers (6a, 6b, 7a, 7b) according to the collected group codes on the display device as a graphical representation of the selected grouping system, and wherein the first grouping system groups the plurality of the amplifiers (6a, 6b, 7a, 7b) based on locations of the respective amplifiers, and the second grouping system groups the plurality of the amplifiers (6a, 6b, 7a, 7b) based on performances of the respective amplifiers (6a, 6b, 7a, 7b), and the display control section is adapted to display the tree diagram of the amplifiers (6a, 6b, 7a, 7b) sorted in terms of the locations thereof when the first grouping system is selected, and displays the tree diagram of the amplifiers (6a, 6b, 7a, 7b) sorted in terms of the performances thereof when the second grouping system is selected. a selecting section adapted to select one of a plurality of grouping systems of the devices, each of the devices allocated to at least a first and second grouping system, wherein the display control section is adapted to select one of the first grouping system and the second grouping system so as to display the tree diagram of the devices corresponding to only the selected one of the first grouping system and the second grouping system, characterized in that said devices are amplifiers (6a, 6b, 7a, 7b) provided to process audio signals, and have at least a first group code corresponding to the first grouping system and second group code corresponding to the second grouping system; and in that said apparatus further comprises: a collecting section adapted to collect the group code corresponding to the selected grouping system, selected by the display control section from each of the amplifiers (6a, 6b, 7a, 7b) through the network; wherein the display control section is adapted to display a tree diagram of the amplifiers (6a, 6b, 7a, 7b) according to the collected group codes on the display device as a graphical representation of the selected grouping system, and wherein the first grouping system groups the plurality of the amplifiers (6a, 6b, 7a, 7b) based on locations of the respective amplifiers, and the second grouping system groups the plurality of the amplifiers (6a, 6b, 7a, 7b) based on performances of the respective amplifiers (6a, 6b, 7a, 7b), and a collecting section adapted to collect the group code corresponding to the selected grouping system, selected by the display control section from each of the amplifiers (6a, 6b, 7a, 7b) through the network; wherein the display control section is adapted to display a tree diagram of the amplifiers (6a, 6b, 7a, 7b) according to the collected group codes on the display device as a graphical representation of the selected grouping system, and wherein the first grouping system groups the plurality of the amplifiers (6a, 6b, 7a, 7b) based on locations of the respective amplifiers, and the second grouping system groups the plurality of the amplifiers (6a, 6b, 7a, 7b) based on performances of the respective amplifiers (6a, 6b, 7a, 7b), and the display control section is adapted to display the tree diagram of the amplifiers (6a, 6b, 7a, 7b) sorted in terms of the locations thereof when the first grouping system is selected, and displays the tree diagram of the amplifiers (6a, 6b, 7a, 7b) sorted in terms of the performances thereof when the second grouping system is selected.