The low layer attributes describe the bearer capabilities which support the teleservice. These low layer attributes and their values are the same as presented in Annex A: List of definitions of attributes and values used for bearer services.

The general attributes are the same as presented in Annex A: List of definitions and values used for bearer services.

This Annex describes the conditions under which a given mobile subscriber (station) is considered as "busy". In general, this occurs whenever the resources associated with that UE (and needed to successfully complete the call) exist but are not available for that call. The description is based on the busy definition in the ISDN (CCITT Recommendation I.221). In addition, the operation of some Supplementary Services occurs when certain of these resources are busy. Therefore, these "resources busy" are also described herein. This Annex does not cover the cases, when network resources not associated with a given destination are unavailable, or when such resources are out-of-service or otherwise non-functional.

This condition occurs, when a call is about to be offered, if the information (i.e. traffic) channel is busy and the maximum number of total calls has been reached (see note). This condition also occurs, when a call is about to be offered and an already on-going call attempt (incoming or outgoing) is in the establishing phase, i.e. not yet active. When NDUB condition occurs, the PLMN will clear the call and indicate "busy" back towards the calling subscriber (see also clause 4). 3GPP TS 22.135 defines NDUB for Multicall environment.

This condition occurs when a call is offered to a user equipment and the UE responds "user busy" because the subscribers resources (terminal or person using them) are busy. Then the PLMN will clear the call with the indication "busy" back towards the calling subscriber (see also clause 4).

A mobile subscriber is considered to be busy if either a "Network Determined User Busy" or a "User Determined User Busy" condition occurs. Some supplementary services (e.g. Call Forwarding on Busy) may cause the call not to be cleared when a busy condition occurs.

This Annex specifies the service requirements for call set-up, both Mobile originated and mobile terminated, in a network, including the establishment of radio contact.

When an UE wishes to start a call and there is no existing radio connection, it requests a signalling channel. When such a signalling channel has been allocated to the UE, the UE can transfer the call set-up information. A traffic channel may be allocated at any time before the network informs the UE that the remote user has answered. For a call to be set up, certain information needs to be sent by the UE to the network, defining the call. This information may be provided as default by the MS, it may be derived from the SIM/USIM or be entered by the user either directly into the UE or from a DTE by using the DTE/DCE Interface. The following information is sent. Where necessary, default values will generally be inserted by the UE if not directly specified by the user. The Teleservice Emergency Calls are set up using a special procedure not using the fields described in this clause (except for the Bearer Capability).

Using the procedures described in TS 22.011, the network knows the location area where the UE is positioned. If the UE is not already in two way radio communication with the network, the network pages the MS. Upon receiving its page message, the UE establishes communication with the selected cell. The network then allocates a channel which is used for signalling and sends call set-up information to the UE. A traffic channel may be allocated at any instant until just after the call is answered by the UE. The network indicates to the UE that it wishes to offer the UE a call. This notification includes the proposed bearer capability information, where available (see clause D.2.5).

Indications of call progress, such as ringing, engaged, unobtainable, and no radio channel, may in principle be verbal message, tones, displayed text or graphical symbols. Which combination of these applies may depend on the message, the UE and selection by the user or PLMN operator. However, verbal announcements will generally be reserved for situations which are peculiar to a mobile network, where users may be unfamiliar with any tone chosen to indicate conditions such as "call diversion" or "subscriber not available". It may also be desirable to add comfort indications (e.g. tones, noise, music, clicks) while a call is being connected, since silence may cause an unfamiliar user to believe that nothing is happening. Generally, on data calls, and on the data part of alternate speech/data or speech-followed-by-data calls, PLMN generated network tones and announcements should be muted.

In present networks, both fixed and cellular, the language of recorded announcements and displayed information is invariably that of the country of origin. However, this is generally undesirable in a multi-lingual environment such as is encountered on a global network with international roaming. It is therefore probably desirable to minimise the number of such announcements. Advanced UEs may be designed which have the ability to generate announcements in the form desired by the user, e.g. in the language preferred by the user. In this case, it becomes necessary to block any verbal announcements sent from the network towards the UE, to avoid clashes with those generated by the UE. The UE may be allowed to block in-band announcements in case appropriate announcements according to the Cause Information Elements (F.3) can be generated. The default setting of the UE shall be "non blocking", which could be set by MMI command to "blocking". Announcements generated by the PLMN and sent to callers to that PLMN will generally be in the language of the PLMN. However, on some fixed networks it will be possible for the message to be signalled back to the caller's local exchange, which will then generate the announcement in its local language.

The Cause Information Elements are listed and defined in TS 24.008. This Annex lists these elements and indicates which supervisory tone should be generated in response. It should be noted that some conditions (e.g. radio path not available, dropped call) may be deduced by the UE, rather than signalled explicitly over the air interface. All causes not listed below should result in the generation of tone 6. In case of multiple calls a tone should only be generated if it does not disturb an ongoing active call. "-" indicates no tone required.