Siemens I-SURF manual Isdn Access, Features, Pabx or Multiple Device Access?, Access Type Pabx

3. Basics of ISDN

3.3 ISDN Access

Converting a standard analog phone line to ISDN has become very simple these days. The existing phone line can simply be changed over to ISDN at a specified point in time. Since ISDN uses existing telephone cables, the telephone company does not need to run any new lines to your house or office.

At the end of the phone line you need an NTBA (network terminator/bus adapter) to convert the two-wire signals for the four-wire ISDN S0 bus.

3.4 Features

ISDN offers a great variety of features, especially for voice communications. The basic functions, however – establishing and terminating connections – are usually quite sufficient for data communications. Consult your ISDN service provider for available features.

3.5 PABX or Multiple Device Access?

Depending on how you wish to use ISDN, there are two types of ISDN basic access

PABX access

Multiple device access

3.6 Access Type: PABX

PABX access always requires a PABX to be connected. All subsequent terminal devices are connected to the PABX as extensions. PABX can also handle analog terminal devices. You will receive a block of subscriber numbers with several direct extension numbers, allowing individual terminal devices to be addressed (dialed) directly.

To connect an ISDN terminal adapter to ISDN via PABX access, you need a PABX with an internal S0 bus.

3.7 Access Type: Multiple Device

Up to 8 terminal devices can be connected to the S0 bus of each multiple device access. Two of them can establish a connection at the same time, each using one B channel.

You will be assigned several Multiple Subscriber Numbers (MSNs) for your multiple device access. By assigning different MSNs to different devices on the S0 bus, you can address these directly.

10