This International Standard specifies the service description and control aspects, including functional capabilities and

information flows, of standardised circuit-mode bearer services which may be supported by a Private Integrated Services

Network (PISN).

This International Standard includes the following basic services:

_ Circuit-mode 64 kbit/s unrestricted 8 kHz structured bearer service category;

_ Circuit-mode 64 kbit/s 8 kHz structured bearer service category usable for speech information transfer;

_ Circuit-mode 64 kbit/s 8 kHz structured bearer service category usable for 3,1 kHz audio information transfer.

A PISN shall support at least one of the above three bearer services to conform with this International Standard.

The scope of this International Standard does not include:

_ the negotiation of service at call establishment time,

_ the change of service during a call, and

_ unidirectional services.

This International Standard includes optional procedures for the provision of functions equivalent to the following public ISDN

supplementary services: Subaddress and Multiple Subscriber Number.

NOTE 1 - Supplementary services and other bearer services which can be used in conjunction with 64 kbit/s circuit switched bearer services

specified in this International Standard are dealt with in other standards.

NOTE 2 - Service specifications are based on information concerning the corresponding public ISDN service available at the time of

publication of this International Standard.

NOTE 3 - ITU-T treat Subaddressing and Multiple Subscriber Number as supplementary services.

NOTE 4 - The use of the Direct Dial In supplementary service of a public ISDN for calls incoming to a PISN from a public ISDN is regarded

as part of the basic services in a PISN.

NOTE 5 - The use of the Calling Line Identification Presentation and Connected Line Identification Presentation supplementary services of a

public ISDN for obtaining the Originating Number or the Connected Number of a call from or to a public ISDN is regarded as part of the

basic services in a PISN.

NOTE 6 - The provision (either explicitly or implicitly) by the user to the network, of its own number (Originating Number or Connected

Number), and the provision of an Originating Number or a Connected Number by a PISN to another network is a part of the basic services in

a PISN and not a part of the Calling Line Identification Presentation and Connected Line Identification Presentation supplementary services.

Those supplementary services are concerned only with the presentation of the number from the network to the served PISN user.