The PG/Service interface serves as feedback-free measuring point for measurements with PB-QONE/PROFtest II/PB-INspektor® NT can also be used as programming interface. The plug is completely shielded by the metal-coated casing. The plug for the terminating resistor that is acces- sible from outside, disconnects the outgoing segment when being in ON position. The design meets the Fast Connect requirement. The integrated 4 LEDs (Power, TxD, Termination, Error) allow a quick diagnosis of the bus status. With the Error LED, for example reflections and missing terminating resistors are signalled.