Eicon Networks ISDN NT1 Specifikace stáhnout pdf (Strana 54)

Remember that MLPPP is not the same two separate PPP links. MLPPP is a single connection which uses

more than one data link. Two PPP connections are two separate connections to two independent

destinations.

PBX or PABX

PBX stands for Private Branch Exchange. PABX means Private Automatic Branch Exchange. Nowadays,

these both mean the same thing.

This is a telephone exchange as would be used within an office to connect a number of internal users to a

(usually) smaller number of outside lines on the public network. They can range in size from very small (two

outside lines and maybe eight extensions) to very large (hundreds of outside lines and thousands of

extensions).

This expression covers both conventional (analogue) exchanges and those supporting ISDN.

ISPBX

This stands for Integrated Services Private Branch Exchange.

This is a telephone exchange as would be used within an office to connect a number of internal users to a

(usually) smaller number of outside lines on the public network. They can range in size from very small (two

outside lines and maybe eight extensions) to very large (hundreds of outside lines and thousands of

extensions).

The public network lines for an ISPBX must be ISDN. The extensions may be served by an internal ISDN or

a conventional analogue telephone network, or both.

ISPBXs are a source of many ISDN problems, because they may be configured in so many different ways

and because the ISDN implementation is sometimes incorrect. When diagnosing ISDN connectivity

problems, it is always best to test your connection on a public ISDN line before calling for support.

Group 4 Fax

Group 4 fax is a method for sending documents at high speed. It only works on ISDN lines and can only

communicate with another Group 4 Fax machine. In contrast with Group 3 which might need as few as 30

seconds to transmit a single page, Group 4 needs only 3 to 5 seconds for the same page.

Group 4 fax machines are quite expensive and very few are installed compared with the number of Group 3

(analogue) fax machines. There are also a number of software packages which emulate a Group 4 fax

machine.

Bearer Capabilities

This is a mechanism by which a user can inform the ISDN of the protocol that he is using in a B channel.

Strictly speaking, the Bearer Capability is one of three mechanisms that are used to communicate this

information. However, the other two mechanisms (called High Layer Compatibility and Low Layer

Compatibility) are always used in conjunction with Bearer Capabilities, so they are often known collectively

as bearer capabilities. The High Layer Compatibility and Low Layer Compatibility are used to provide

additional details about the B channel protocol. On this page, Bearer Capabilities (capitalised) refers to the

mechanism, bearer capabilities (lower case) refer to the protocol in use.

When a user requests a connection through an ISDN, he is obliged to specify the Bearer Capabilities. If he

does not, his request is rejected. If he is using a protocol that the ISDN does not understand he will specify

that the data is transparent (or unstructured). High Layer Compatibility and Low Layer Compatibility are both

optional.

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Eicon Networks ISDN NT1 Specifikace Strana 54