s Run traffic and bill The first step in Basic Rate testing is to establish the integrity of the physical connection between the subscriber's S interface, via the Network Terminator, to the exchange, or simply the U interface Quality of service connection between the Network Terminator and the exchange. In service monitor The following physical parameters can be measured: 1. Correct wiring polarity of the pairs, presence of out of specifi- cation hazardous voltages, and insulation resistance. Figure 61.16 Type of test depends on stage of maturity Presence of phantom power, which is provided by the network as a common mode potential between the two pairs of the S interface. The level and polarity of this voltage can be measured. ance. In installation and commissioning, transmission quality begins to play an important part, and in maintenance work, the 3. Presence of, and accuracy of, the clock which is provided by the network. specification is assumed, and long term performance is the issue. Therefore, as a particular installation or service matures, the trend Indication and manipulation of the information states by which is from conformance testing to transmission quality testing. Before the physical communication is set up. the 1990s, ISDN was largely a developing technology, but as more 5. Impedance and insertion loss of the line. real installations come into service, commissioning and mainten- 6. The relationship of the longitudinal balance of the circuit to the ance performance testing is rapidly expanding. frequency of transmitted signals, for manual or automatic com- parison with the limits specified by CCITT 1.430. 7. The shape, balance, delay and jitter of transmitted pulses. 61.5.4.2 Transmission test connection methods A functional test of each transmission component, out of service, 61.5.5.3 Basic Rate test call set up can prove the integrity of the component while reducing the risk of damage or impairment to the network due to the connection of In order to carry out transmission tests, a call has firs