M12 terminating resistors are used to terminate PROFIBUS segments usually in the place where the last station (with M12 connectors) on the segment is located. This kind of station doesn't usually feature an integrated segment terminator. It's exactly for this reason that the M12 terminating resistor is connected to the station's output port.
M12 terminating resistor for PROFIBUS networks.
M12 female terminating resistor for PROFIBUS, DeviceNet and CANopen networks.