Are there any tests to classify and ascertain that the service provider has commissioned an ISDN BRI line to optimum standards? I believe there are some parameters such as L1 to L8, but not much info is available.
What is the ideal DC voltage across the NT1? In practice, we have found that 93 - 98 volts for Fujitsu FETEX exchanges and 98 - 104 volts for Siemens exchanges works well. What are the ideal values?
There are several products for working with WAN links including ISDN. Your provider can also help you by providing you with the proper reports - most of them will provide them to you for little or no charge. The
Basic Rate Interface (BRI)
service offers two
(2B+D). BRI B-channel service operates at 64 Kbps and is meant to carry user data; BRI D-channel service operates at 16 Kbps and is meant to carry control and signaling information, although it can support user data transmission under certain circumstances. The D-channel signaling protocol comprises Layers 1 through 3 of the OSI reference model. BRI also provides for framing control and other overhead, bringing its total bit rate to 192 Kbps.
The BRI physical layer specification is International Telecommunication Union-Telecommunications Standards Section (ITU-T), formerly the Consultative Committee for International Telegraph and Telephone (CCITT) I.430.
As for voltage - there are many factors here and this question would best be answered by the manufacturer.