A portable device maintenance support apparatus for maintenance work of a field device, said portable device maintenance support apparatus being connectable to the field device via a hybrid communication network, said portable device maintenance support apparatus comprising: one set of terminals (S101-S108) including a first pair of terminals (S101, S103), a second pair of terminals (S102, S104), and the other terminals (S105-S108), wherein the first pair of terminals (S101, S103) is configured to be connectable to the hybrid communication network, which is based on one of at least two hybrid communication protocols, in which a digital signal is superimposed onto an analog signal, wherein the second pair of terminals (S102, S104) is used to perform data receiving and transmitting in accordance with the one of the hybrid communication protocols via the first pair of terminals (S101, S103), the hybrid communication network being performed between the portable device maintenance support apparatus and said field device, wherein said digital signal includes at least device information of said field device; and wherein the first pair of terminals (S101, S103) is configured to be used for any of the plurality of at least two hybrid communication protocols, wherein a resistance (105c, 115a), as a current limiting element, is connected to only one of the terminals of the first pair of terminals (S101, S103); and wherein said portable device maintenance support apparatus further comprises a measurement circuit configured to measure a second voltage across the resistance (105c, 115a) via two of the terminals(S107, S108) of the other terminals(S105-S108) and a first voltage between the pair of terminals (S101, S103) via two of the terminals (S105, S106) of the other terminals (S105-S108) for selecting one of the at least two hybrid communication protocols and detecting abnormally communication. one set of terminals (S101-S108) including a first pair of terminals (S101, S103), a second pair of terminals (S102, S104), and the other terminals (S105-S108), wherein the first pair of terminals (S101, S103) is configured to be connectable to the hybrid communication network, which is based on one of at least two hybrid communication protocols, in which a digital signal is superimposed onto an analog signal, wherein the second pair of terminals (S102, S104) is used to perform data receiving and transmitting in accordance with the one of the hybrid communication protocols via the first pair of terminals (S101, S103), the hybrid communication network being performed between the portable device maintenance support apparatus and said field device, wherein said digital signal includes at least device information of said field device; and wherein the first pair of terminals (S101, S103) is configured to be used for any of the plurality of at least two hybrid communication protocols, wherein a resistance (105c, 115a), as a current limiting element, is connected to only one of the terminals of the first pair of terminals (S101, S103); and wherein said portable device maintenance support apparatus further comprises a measurement circuit configured to measure a second voltage across the resistance (105c, 115a) via two of the terminals(S107, S108) of the other terminals(S105-S108) and a first voltage between the pair of terminals (S101, S103) via two of the terminals (S105, S106) of the other terminals (S105-S108) for selecting one of the at least two hybrid communication protocols and detecting abnormally communication.