A redundant half-duplex fieldbus coupler for bi-directionally coupling of two half-duplex fieldbus segments (S1, S2) each having a first half-duplex channel segment (a1, a2) and a second half-duplex channel segment (b1, b2) redundant to one another, the fieldbus coupler comprising: two transceiver units (T_a1, T_b1), wherein a respective one of the two transceiver units (T_a1, T_b1) is connected with a respective one of the two channel segments (a1, b1) of one of the two fieldbus segments (S1, S2); two further transceiver units (T_a2, T_b2), wherein a respective one of the two further transceiver units (T_a2, T_b2) is connected with a respective one of the two channel segments (a2, b2) of the other one of the two fieldbus segments (S1, S2); and wherein each transceiver unit (T_a1, T_a2, T_b1, T_b2) comprises a receiver (Rx) to receive data from the channel segment (a1, b1, a2, b2) to which the respective transceiver unit (T_a1, T_a2, T_b1, T_b2) is connected and a transmitter (Tx) to transmit data to the channel segment (a1, b1, a2, b2) to which the respective transceiver unit (T_a1, T_a2, T_b1, T_b2) is connected; wherein the fieldbus coupler further comprises: a decider unit (D_a1, D_a2, D_b1, D_b2) configured to detect if any one of the two channel segments (a1, b1, a2, b2) of any one of the two fieldbus segments (S1, S2) is defective, which renders the respective fieldbus segment defective, and, if a defective fieldbus segment having a defective channel segment is detected, to cause that the receiver (Rx) of the transceiver unit (T_a1, T_a2, T_b1, T_b2), which is connected to the defective channel segment of the defective fieldbus segment, is decoupled from the transmitter (Tx) of the transceiver unit (T_a1, T_a2, T_b1, T_b2) which is connected to the corresponding channel segment of the other fieldbus segment, and that the receiver (Rx) of the transceiver unit (T_a1, T_a2, T_b1, T_b2), which is connected to the intact channel segment of the defective fieldbus segment, is coupled with the respective transmitter (Tx) of both transceiver unis (T_a1, T_a2, T_b1, T_b2) of the other fieldbus segment. two transceiver units (T_a1, T_b1), wherein a respective one of the two transceiver units (T_a1, T_b1) is connected with a respective one of the two channel segments (a1, b1) of one of the two fieldbus segments (S1, S2); two further transceiver units (T_a2, T_b2), wherein a respective one of the two further transceiver units (T_a2, T_b2) is connected with a respective one of the two channel segments (a2, b2) of the other one of the two fieldbus segments (S1, S2); and wherein each transceiver unit (T_a1, T_a2, T_b1, T_b2) comprises a receiver (Rx) to receive data from the channel segment (a1, b1, a2, b2) to which the respective transceiver unit (T_a1, T_a2, T_b1, T_b2) is connected and a transmitter (Tx) to transmit data to the channel segment (a1, b1, a2, b2) to which the respective transceiver unit (T_a1, T_a2, T_b1, T_b2) is connected; wherein the fieldbus coupler further comprises: a decider unit (D_a1, D_a2, D_b1, D_b2) configured to detect if any one of the two channel segments (a1, b1, a2, b2) of any one of the two fieldbus segments (S1, S2) is defective, which renders the respective fieldbus segment defective, and, if a defective fieldbus segment having a defective channel segment is detected, to cause that the receiver (Rx) of the transceiver unit (T_a1, T_a2, T_b1, T_b2), which is connected to the defective channel segment of the defective fieldbus segment, is decoupled from the transmitter (Tx) of the transceiver unit (T_a1, T_a2, T_b1, T_b2) which is connected to the corresponding channel segment of the other fieldbus segment, and that the receiver (Rx) of the transceiver unit (T_a1, T_a2, T_b1, T_b2), which is connected to the intact channel segment of the defective fieldbus segment, is coupled with the respective transmitter (Tx) of both transceiver unis (T_a1, T_a2, T_b1, T_b2) of the other fieldbus segment. a decider unit (D_a1, D_a2, D_b1, D_b2) configured to detect if any one of the two channel segments (a1, b1, a2, b2) of any one of the two fieldbus segments (S1, S2) is defective, which renders the respective fieldbus segment defective, and, if a defective fieldbus segment having a defective channel segment is detected, to cause that the receiver (Rx) of the transceiver unit (T_a1, T_a2, T_b1, T_b2), which is connected to the defective channel segment of the defective fieldbus segment, is decoupled from the transmitter (Tx) of the transceiver unit (T_a1, T_a2, T_b1, T_b2) which is connected to the corresponding channel segment of the other fieldbus segment, and that the receiver (Rx) of the transceiver unit (T_a1, T_a2, T_b1, T_b2), which is connected to the intact channel segment of the defective fieldbus segment, is coupled with the respective transmitter (Tx) of both transceiver unis (T_a1, T_a2, T_b1, T_b2) of the other fieldbus segment.