ÿWPCL ûÿ2BJ|xÐ ` ÐÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿH øxÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÐ °°°è ÐÑ Âx„|ü@Ž ÑÐ Å°6Ø'°6Ø'Å ÐÕ-IÐ ` Ð(3247) -ÕÕ-IÐ ` Ð(3247) -Õ Recommendation Q.83 © Call completion supplementary services Ð ( Ð ÓÓÃÃPageÄÄ Ð À Ð1. Call waiting................................................... 6 2. Call hold...................................................... 29 3. Completion of call to busy subscriber (CCBS) (under study)..... 41 Õ>Ï ÁàÐLÁ©  ©ƒ ÁàÐHÁAP IX©98©Eƒ >ÕÕ>Ï ÁàÐLÁ©  ©ƒ ÁàÐHÁAP IX©98©Eƒ >ÕÐ °èè ÐÃÃRecommendation Q.83ÄÄ ÁàÐ:ÁCALL COMPLETION SUPPLEMENTARY SERVICESƒ 1.ÁHÁÃÃCall waitingÄÄ 1.1ÁHÁÃÃGeneralÄÄ ÁHÁThis Recommendation provides information on the functions in ISDN entities and the information flows between the entities which are required to provide the call waiting supplementary service. ÁHÁThe call waiting supplementary service will permit a subscriber to be notified of an incoming call (as per basic call procedures) with an indication that no interface information channel is available. ÁHÁThe user then has the choice of accepting, rejecting or ignoring the waiting call (as per basic call procedures). 1.2ÁHÁÃÃDescriptionÄÄ 1.2.1ÁHÁÃÃGeneral descriptionÄÄ ÁHÁThe ISDN call waiting service allows notification to subscriber B of the incoming call to be out©of©band and this is the assumed case for this definition. In addition, as a service provider option audible in©band indications may be provided. ÁHÁWhere this option is provided, the application of in©band indications, in relation to particular call types and channels, is for further study. Where applied, tones should be in accordance with Recommendation E.180. ÁHÁThe maximum number of calls that can be handled (e.g. active, held, alerting, waiting) for each ISDN number on a given interface is specified at subscription time. 1.2.2ÁHÁÃÃQualifications on the applicability to telecommunication servicesÄÄ Ð X ÐÁHÁThis supplementary service is considered meaningful when applied to the telephony teleservice, speech and 3.1 kHz audio bearer services. Furthermore, it may also be meaningful when applied to other services. 1.3ÁHÁÃÃDerivation of the functional model for call waiting serviceÄÄ ÁHÁThe model used for illustrating the call waiting supplementary service procedures is given below: USER A USER B CCA: CC: CC: CC: CCA: Call control Call control Call control Call control Call control agent functions functions functions agent functions functions ÁHÁCCA is the functional entity that serves the user and is responsible for initiating functional requests and interacting with the network. CC is the functional entity within the network that cooperates with its peers to provide the services requested by CCA. ÁHÁrÃÃ1ÄÄ and rÃÃ2ÄÄ are relationships between functional entities wherein information flows occur in order to process call attempts on service requests. 1.4ÁHÁÃÃInformation flow diagramsÄÄ ÁHÁThis section contains the information flow diagram for the successful sequences of call waiting. ÁHÁThe following flow diagrams are identified: ÁHÁ©Âà  ÂFigure 1©1/Q.83: call waiting notification: case 1;ÆÆ ÂHH©Âà  ÂFigure 1©2/Q.83: call waiting notification: case 2;ÆÆ Ð ` Ð ÂHH©Âà  ÂFigure 1©3/Q.83: call waiting notification: case 3;ÆÆ Ð  ÐÂHH©Âà  ÂFigure 1©4/Q.83: call waiting accceptance by clearing theÆÆ Ð ` Ð A call: case 1; Ð € ÐÂHH©Âà  ÂFigure 1©5/Q.83: call waiting acceptance by clearing theÆÆ Ð ` ÐÁHÁÁ  Á A call: case 2; Ð ø ÐÂHH©Âà  ÂFigure 1©6/Q.83: call waiting acceptance by holding theÆÆ Ð ` ÐÁHÁÁ  Á A call: case 1; Ð € ÐÂHH©Âà  ÂFigure 1©7/Q.83: call waiting accceptance by holding theÆÆ Ð ` Ð A call: case 2; ÂHH©Âà  ÂFigure 1©8/Q.83: call waiting rejection;ÆÆ ÂHH©Âà  ÂFigure 1©9/Q.83: call waiting cancellation.ÆÆ 1.4.1ÁHÁÃÃCall waiting terminologyÄÄ Ð À ÐÁHÁThroughout the stage 2 description the following terminology will be used: ÁHÁi)Á   ÁSubscriber B: This is the subscriber who is provided by the ÂHHÂÂX  Ânetwork with call waiting service on a particular interface.ÆÆ Ð ` Ð Ð ° ÐÂHHÂii)Âð   ÂUser at B: This is the one user who reacts to the call waitingÆÆ ÂHHÂÂX  Âat B.ÆÆ Ð ` Ð Ð X ÐÂHHÂÂX  ÂÁ€ HÁiii)Á øÁUser C: This is the user who has originated a call to B which causes the call waiting service to be invoked.ÆÆ Ð ` Ð Ð 8 ÐÂHHÂiv)Âð   ÂOne user at A: This represents a user who is engaged in a call with a user at B (this call can be in any state).ÆÆ Ð ` Ð Ð ( ÐÂHHÂv)Âh   ÂInformation channel control: A terminal that has information channel control is active on a call, is alerting for an incoming call, has an outgoing call in a state following or including the outgoing call proceeding state, or has a call on hold with reservation.ÆÆ Ð ` Ð 1.4.2ÁHÁÃÃCall waiting procedures with successful outcomeÄÄ Ð ( ÐÁHÁThe call waiting procedures with successful outcome are hereafter described by means of generic information flow diagrams. 1.4.2.1Á  ÁCall waiting notification Ð Ð ÐÁHÁThe call waiting notification procedures are given in Figures 1©1/Q.83 to 1©3/Q.83. ÁHÁTwo categories are identified: Ð H ÐÂHHÂi)Âh   ÂFigures 1©1/Q.83 and 1©2/Q.83 describe the case where the served user is notified of an incoming call and the network requires an interface channel to his user access and it has detected that all information channels are in use (no information channel available). ÆÆ Ð ` Ð Ð   ÐÂHHÂii)Âð   ÂFigure 1©3/Q.83 describes the case where the served user is notified of an incoming call and the network requires an interface channel to his user access and it has detected that an existing free information channel, which is the only compatible terminal, is in the busy condition (information channel available).ÆÆÐ ` Ð Ð X ÐÁHÁThe following procedures are valid for call waiting with no information channel available. ÁHÁWhen an incoming call from a user C arrives at the functional entity controlling the access at B and encounters the channel's busy condition and the network determined user busy conditions do not result, then the call shall be offered to B by means of the Setup procedure with the "no information channel" indicated. ÁHÁThe following actions will be taken by the terminals connected to the user B access: ÂHHÂi)Âh   ÂIncompatible terminals will not react.ÆÆ Ð ` Ð Ð H ÐÂHHÂii)Âð   ÂTerminals not presently controlling the information channel that are compatible with the incoming call will respond by initiating the release procedure indicating a no information circuit/channel available condition.ÆÆ Ð ` Ð Ð H ÐÂHHÂiii) Terminals presently controlling the information channel that doÆÆ ÂHHÂÂX  Ânot support the call waiting service and are compatible with the incoming call will respond either by initiating the release procedure indicating a user busy condition or by acting as incompatible terminals (e.g. no reaction).ÆÆ Ð ` Ð Ð € ÐÂHHÂiv)Âð   ÂTerminals presently controlling the information channel that support the call waiting service and that are compatible with the incoming call will respond by initiating the call progress (reporting) procedure and will give a local alert to the human user by giving an audible and/or visual (in©band) indication.ÆÆ Ð ` Ð Ð X ÐÁHÁWhen a positive response is received from the terminals at B within the normal basic call period, that (those) user(s) is (are) being informed about the incoming call, then the calling user at C will be given an indication that the called user(s) is (are) being informed. This will be performed by the network at the B side by sending of the ringing tone; some networks may instead generate a special call waiting tone, provided the bearer capability is either speech or audio 3.1 kHz. In addition, optionally, a call waiting out of band indication may be sent to the C user. ÁHÁÃÃCase 1ÄÄ: Both B Channels busy, one terminal controlling a B Channel supports call waiting. ÁHÁFigure 1©1/Q.83 shows the generic information flow diagram for call waiting notification when the incoming call from user C is delivered at the user B access by broadcast data link without available information channels. ÁHÁThe following user B access terminals are assumed: Ð ÐÂHHÂÂX  ÂÂX øÂÁ€  ÁÁ€ HÁ©Á  ÁTE1:Áx!ÁBeing a compatible terminal not supporting call waiting occupying channel B1 and having a call reference CR1. This terminal is assumed to be located in FE6.ÆÆÐ ` Ð Ð ÐÂHHÂÂX  ÂÂX øÂÁ€  ÁÁ€ HÁ©Á  ÁTE2:Áx!ÁBeing a compatible terminal not presently controlling the information channel. This terminal is assumed to be located in FE6'.ÆÆ Ð ` Ð Ð ÐÂHHÂÂX  ÂÂX øÂÁ€  ÁÁ€ HÁ©Á  ÁTE3:Áx!ÁBeing a compatible terminal supporting call waiting, occupying channel B2 and having a call reference CR2. This terminal is assumed to be located in FE6".ÆÆ Ð ` Ð Ð À ÐÁHÁThe new incoming call from C is assumed to have a call reference CR3. Ð X ÐÁHÁÃÃCase 2ÄÄ: Both B Channels busy, both terminals controlling the B Channels support call waiting. ÁHÁFigure 1©2/Q.83 shows the generic information flow diagram for call waiting notification when the incoming call from user C is delivered at the user B access by broadcast data link without available information channels. ÁHÁThe following user B access terminals are assumed. Ð ÐÂHHÂÂX  ÂÂX øÂÁ€  ÁÁ€ HÁ©Á  ÁTE1:Áx!ÁBeing a compatible terminal supporting call waiting occupying channel B1 and having a call reference CR1. This terminal is assumed to be located in FE6.ÆÆ Ð ` Ð Ð ÐÂHHÂÂX  ÂÂX øÂÁ€  ÁÁ€ HÁ©Á  ÁTE2:Áx!ÁBeing a compatible terminal not presently controlling the information channel. This terminal is assumed to be located in FE6'.ÆÆ Ð ` Ð Ð ÐÂHHÂÂX  ÂÂX øÂÁ€  ÁÁ€ HÁ©Á  ÁTE3:Áx!ÁBeing a compatible terminal supporting call waiting, occupying channel B2 and having a call reference CR2. This terminal is assumed to be located in FE6".ÆÆ Ð ` Ð Ð À ÐÁHÁThe new incoming call from C is assumed to have a call reference CR3. Ð X ÐÁHÁÃÃCase 3ÄÄ: One B Channel busy, the terminal controlling the busy B Channel supporting call waiting. ÁHÁFigure 1©3/Q.83 shows the generic information flow diagram for call waiting notification when the incoming call from user C is delivered at the user B access by broadcast data link with an available information channel, but the only compatible terminal is presently controlling an information channel. ÁHÁIf the thus compatible terminal has call waiting facilities available, it alerts its user (audible or visible indication) and notifies the network (REPORT). The user then can decide whether to accept the waiting call or not. 1.4.2.2Á  ÁCall waiting acceptance ÁHÁIf a user at B requests, within a specified period, to connect to the waiting call, two procedures may be required by user B with regard to the active call with a user at A. Ð ° ÐÂHHÂi)Âh   ÂProcedure one will terminate the specified active call with a user at A, while the call between a user at C and the user at B is completed in the normal manner (see Figures 1©4/Q.83 and 1©5/Q.83).ÆÆÐ ` Ð Ð Ð ÐÂHHÂii)Âð   ÂProcedure two will place the specified active call with a user at A into a held state, while the call between a user at C and the user at B will be completed in the normal manner. The previously active call between a user at A and the user at B is put into the held state. From this state other supplementary services, for example, three party service may be used (see Figures 1©6/Q.83 and 1©7/Q.83).ÆÆ Ð ` Ð Ð X ÐÂHH This acceptance provokes the initiation of a Hold sequence by the terminal to the network. The network will hold the previous call between a user at A and the user at B, while the waiting call from a user at C will be connected by a Setup response/confirm sequence.ÆÆ Ð ` Ð Ð Ð ÐÁHÁÂX  ÂSince more than one terminal controlling the information channels can respond positively to a call waiting offering, the network will subsequently apply a clear procedure to the remaining terminals having responded positively after having received the Setup response/confirmation order.ÆÆ 1.4.2.3Á  ÁCall waiting rejection ÁHÁThe user at B can also, within the specified period, reject the new incoming call from user C. In this case, call clearing procedures (see Figure 1©8/Q.83) will apply at the basic access interface. ÁHÁIf the terminals controlling the information channels have initiated the Report (alerting) procedures, the network will wait after the reception of the first release sequence from a terminal for the possible reaction of the other terminal. If all the users reject the waiting call, the network shall initiate the clearing of the call indicating the user determined busy condition of the called users to the calling user C. 1.4.2.4Á  ÁCall waiting notification ignored ÁHÁIf the specified period expires without any acceptance from B of the incoming call, then the network shall inform B of this situation and also inform C that this call cannot be connected. ÁHÁNormal release applies to the call attempt from C by sending an appropriate clearing indication to the calling user (see Figure 1©9/Q.83). ÁHÁA rejection of the waiting call by one terminal will not stop the call waiting timer, as another terminal may accept the waiting call within the specified period. 1.5ÁHÁÃÃSDL diagrams for functional entitiesÄÄ ÁHÁThis section contains the SDL diagrams for the network function entity FE5. The entire SDL is a variation of the basic call rÃÃ2ÄÄ © rÃÃ1ÄÄ CALL SENT state. ÁHÁThe relationships "rÃÃ1ÄÄ" and "rÃÃ2ÄÄ" have been deleted in functional entity FE5 between functional entities FE4 (rÃÃ2ÄÄ) and FE6 (rÃÃ1ÄÄ), see section 3.1.3. ÃÃNote 1ÄÄ © If the call waiting flag is set then the "no information channel" indication should be included. When not set, normal call offering procedures apply. Depending on the terminal configuration the set up message will be delivered by point©to©point or by broadcast data link. ÃÃNote 2ÄÄ © When user network interface channels are free and the call waiting service is subscribed, some implications may occur with regard to channel negotiation procedure complications, in particular with exclusive channel negotiation. ÃÃNote 3ÄÄ © This is a substate of the "rÃÃ2ÄÄ © rÃÃ1ÄÄ CALL SENT" state of the basic service description. ÃÃNote 4ÄÄ © This timer is the same as for the basic call service. ÃÃNote 5ÄÄ © Other possible supplementary services may apply; e.g. CCBS, CFB. ÃÃNote 1ÄÄ © Optionally compatible busy terminals not having call waiting may not respond. ÃÃNote 2ÄÄ © Timer 1 expiration is dependent on terminal configuration being either point©to©point or broadcast link. ÃÃNote 3ÄÄ © This is a substate of the "rÃÃ2ÄÄ © rÃÃ1ÄÄ CALL SENT" state of the basic service description. ÃÃNote 4ÄÄ © The status may either indicate "USER BUSY" (for compatible busy terminals not having call waiting); or "no©circuit©or©channel available" (for free compatible terminal). ÃÃNote 5ÄÄ © If the call waiting flag is not set this is the normal call service supervision timer which controls the time©out for Report (Alert) without receipt of the setup confirmation, and specifies the period the network will wait for a response, from party B, to the offered call from user C. ÃÃNoteÄÄ © This is a substate of the "rÃÃ2ÄÄ © rÃÃ1ÄÄ CALL SENT" state of the basic service description. Ð h ÐÃÃNote 1ÄÄ © Timer 2 is not stopped and supervises the receipt of the consequent set up confirmation. ÃÃNote 2ÄÄ © This is a substate of the "rÃÃ2ÄÄ © rÃÃ1ÄÄ CALLÃà ÄÄSENT" state, of the basic service description. 1.6ÁHÁÃÃFunctional entity actionsÄÄ ÁHÁThe functional entity actions are identical to the actions required for the circuit mode switched bearer services speech, 3.1 kHz audio unrestricted and alternate speech/unrestricted information transfer. 1.7ÁHÁÃÃAllocation of functional entities to physical locationsÄÄ ÁHÁThe following allocation of functional entities to physical locations of the call waiting supplementary service are applicable: ÁHÁi)Á   ÁÃÃCase 1ÄÄ FE1 FE3 FE4 FE5 FE6 FE2 FE7 FE8 LE TE TE LE TR ÁHÁFE1, FE2 and FE6 are the functional entities which represent the users of the call waiting supplementary service (e.g. may be physically located in TE or NT2 equipment). FE1 represents user A, FE2 user C and FE6 user B. FE6 is the service requesting terminal and FE1 and FE2 the remote terminals. ÁHÁFE3, FE4, FE5, FE7 and FE8 are the functional entities which represent the network functions. ÁHÁFE5 represents the network access providing exchange, FE4 and FE8 the transit exchanges, FE3 and FE7 the remote local exchanges. ÁHÁii)Á   ÁÃÃCase 2ÄÄ FE1 FE3 FE4 FE5 FE6 FE2 FE7 FE8 NT2 TE TE LE LE (PRA) (BA) ÁHÁFE1, FE2, FE5 AND FE6 are the functional entities which represent the users of the call waiting supplementary service. FE1 represents user A, FE2 user C. ÁHÁFE6 is the service requesting terminal while FE5 represents the service providing NT2. ÁHÁFE3, FE4, FE7 and FE8 are the functional entities which represent the local network functions. ÁHÁiii)Á øÁÃÃCase 3ÄÄ FE1 FE3 FE4 FE5 FE6 FE2 FE7 FE8 LE TE NT2 LE ÁHÁFE1, FE2, FE3, FE6 and FE7 are the functional entities which represent the users of the call waiting supplementary service. FE1 and FE3 represent user A, FE2 and FE7 represent user C while FE6 represents user B. ÁHÁFE6 is the service requesting terminal, FE1 and FE2 the remote terminals and FE3 and FE7 the remote NT2s. ÁHÁFE4, FE5 and FE8 are the functional entities which represent the local network functions. ÁHÁiv)Á   ÁÃÃCase 4ÄÄ FE1 FE3 FE4 FE5 FE2 FE7 FE8 NT2 FE6 NT2 LE LE ÁHÁFE1, FE2, FE5 and FE6 are the functional entities which represent the users of the call waiting supplementary service. FE1 represents user A, FE2 user C and FE5 and FE6 user B, FE6 being the service requesting terminal. ÁHÁFE5 being the service providing NT2 and FE1 and FE2 the remote terminals. ÁHÁFE3, FE4, FE7 and FE8 are the functional entities which represent the local network functions. ÁHÁv)Á   ÁÃÃCase 5ÄÄ FE1 FE3 FE4 FE5 FE2 FE7 FE8 TE TE/NT2 LE ÁHÁFE1, FE2 and FE5 are the functional entities which represent the users of the call waiting supplementary service. FE1 represents user A, FE2 user C and FE5 and FE6 user B, FE5 is as well as the service requesting as the service providing terminal while FE1 and FE2 are the remote terminals/NT2s. ÁHÁFE3, FE4, FE7 and FE8 are the functional entities which represent the local network functions. 2.ÁHÁÃÃCall holdÄÄ 2.1ÁHÁÃÃIntroductionÄÄ ÁHÁReferences: CCITT Recommendation I.253, ÀÀ 2, Call hold (Stage 1) Service description ÁHÁThis paragraph includes treatment of the network options as described in the Stage 1 service description. Specifically, (1) optional notification to the held party indicating that the call has been placed on hold, and (2) optional notification to the held party that a call has been retrieved. 2.1.1ÁHÁÃÃDefinitionÄÄ ÁHÁThe Call Hold Service allows a user to interrupt communications on an existing call/connection* and then subsequently, if desired, re©establish communications. A B Channel** may or may not be reserved after the communication is interrupted to allow the origination or possible termination of other calls. Reservation must be provided by the service provider as a user option. The Call Hold service includes the Retrieve operation which re©establishes communication on a B Channel between the served user and the held party. ЀÐÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ ÐÐ*   ÃÃNoteÄÄ © The applicability of the hold service to a "call" versus a     "connection" requires further study. **  ÃÃNoteÄÄ © The applicability of this service definition to other access     resources (e.g., H©channels, logical channels) for other services     requires further study. 2.2ÁHÁÃÃDefinition of functional modelÄÄ 2.2.1ÁHÁÃÃFunctional model descriptionÄÄ Áà8KÁFIGURE 2©1/Q.83ƒ Áà8RÁƒ Áà8JÁÃÃFunctional modelÄă ÁHÁr, along with its subscripts, represents different information flow relationships between functional entities. FE3 and FE4 are shown as dashed circles to represent their optional nature in the context of the Call Hold Service. 2.2.1.1Á  ÁDescription of Functional Entity 1 ÁHÁFunctional Entity 1 supports the following functionality: ÁHÁ1)Âh   Âaccess the service providing capabilities of Functional Entity 2 by way of functional service requests (e.g., hold request, retrieve request);ÆÆ ÁHÁ2)Âh   Âreceive functional indications relating to the call from Functional Entity 2 and relay them to the "user" of the call (e.g., hold confirmation, retrieve confirmation).ÆÆ 2.2.1.2Á  ÁDescription of Functional Entity 2 ÁHÁFunctional Entity 2 supports the following functionality: ÁHÁ1)Âh   Âreceive the functional service requests from Functional Entity 1 and relay them into the network (e.g., receive the hold request from Functional Entity 1 and relay an optional notification of the held call toward user B);ÆÆ ÁHÁ2)Âh   Âperform the holding function (Functional Entity action 201);ÆÆ ÁHÁ3)Âh   Âsend functional indications relating to the call to Functional Entity 1 (e.g., hold confirmation, retrieve confirmation);ÆÆ ÁHÁ4)Âh   Âreserve an information channel, if reservation is subscribed to (Functional Entity action 203);ÆÆ ÁHÁ5)Âh   Âperform reservation management (Functional Entity action 204);ÆÆ ÁHÁ6)Âh   Âperform the retrieve function (Functional Entity action 202).ÆÆ 2.2.1.3Á  ÁDescription of Functional Entity 3 ÁHÁFunctional Entity 3 supports the following functionality: Ô k+ ÔŒÁHÁ1)Âh   Âreceive the optional notification of call hold and the optional notification of retrieval and relay them toward Functional Entity 4;ÆÆ ÁHÁ2)Âh   Âidentify the call at the FE3/FE4 interface that the optional notifications apply to (Functional Entity action 205).ÆÆ 2.2.1.4  Description of Functional Entity 4 ÁHÁFunctional Entity 4 supports the following functionality: ÁHÁ1)Âh   Âreceive the optional notification of call hold and the optional notification of retrieval and inform (relay them to) user B.ÆÆ 2.2.2ÁHÁÃÃRelationship to Basic ServiceÄÄ Áà8KÁFIGURE 2©2/Q.83ƒ Áà8RÁƒ Áà8DÁÃÃRelationship to basic serviceÄă Áà8RÁƒ ÁHÁThe call control agent (CCA) is the functional entity that serves the user and is responsible for initiating functional requests and interacting with the network. Call control (CC) is performed by functional entities within the network to provide the services requested by the CCA. 2.3ÁHÁÃÃInformation flow descriptionÄÄ 2.3.1ÁHÁÃÃInformation flow diagram for successful operationÄÄ Áà8KÁFIGURE 2©3/Q.83ƒ Áà8RÁƒ Áà8;ÁÃÃInformation flow diagram for call hold serviceÄă Áà8RÁƒ 2.3.2ÁHÁÃÃDefinition of individual information flowsÄÄ 2.3.2.1Á  ÁHold request 2.3.2.1.1  Meaning of hold request ÁHÁHold request is the information sent from FE1 to FE2 to request that a call be placed on hold by the network. 2.3.2.1.2  Information content for Hold Request ÁHÁThe following information is contained in the Hold Request: ÁHÁ©Âà  Âan identifier of the call to which the Hold Request applies.ÆÆ 2.3.2.2Á  ÁHold Confirmation 2.3.2.2.1  Meaning of Hold Confirmation ÁHÁHold Confirmation is the information sent from FE2 to FE1 that confirms that a call has been put on hold for the user by the network. 2.3.2.2.2  Information Content for Hold Confirmation ÁHÁThe following information is contained in the Hold Confirmation: ÁHÁ©Âà  Âan identifier of the call to which the Hold Confirmation applies.ÆÆ 2.3.2.3Á  Á(Optional) Notification of Hold 2.3.2.3.1  Meaning of (Optional) Notification of Hold ÁHÁ(Optional) Notification of Hold is the information sent from FE2 towards B indicating that the call between FE1 and FE2 has been placed on hold. 2.3.2.3.2  Information Content for (Optional) Notification of Hold ÁHÁThe following information is contained in the (Optional) Notification of Hold: Ô k+ÔŒÁHÁ©Âà  Âan identifier of the call to which the (Optional) Notification of Hold applies.ÆÆ 2.3.2.4Á  ÁRetrieve Request 2.3.2.4.1  Meaning of Retrieve Request ÁHÁRetrieve Request is the information sent from FE1 to FE2 to request the reconnection of a held call. 2.3.2.4.2  Information Content for Retrieve Request ÁHÁThe following information is contained in the Retrieve Request: ÁHÁ©Âà  Âan identifier of the call to which the Retrieve Request applies;ÆÆ ÁHÁ©Âà  Âan optional indication that:ÆÆ ÁHÁÁ  Á1)ÂhøÂany channel is acceptable for retrieval, orÆÆ ÁHÁÁ  Á2)ÂhøÂa specified channel is preferred for retrieval, orÆÆ ÁHÁÁ  Á3)ÂhøÂa specified channel is exclusively required for retrieval.ÆÆ 2.3.2.5  Retrieve Confirmation 2.3.2.5.1  Meaning of Retrieve Confirmation ÁHÁRetrieve Confirmation is the information sent from FE2 to FE1 that confirms that communications was able to be re©established and that the held call is now reconnected. If an optional indication concerning the B Channel over which communications was to have been re©established was included in the Retrieve Request, then the Retrieve Confirmation serves as an acknowledgement that retrieval was carried out as requested. 2.3.2.5.2  Information Content for Retrieve Confirmation ÁHÁThe following information is contained in the Retrieve Confirmation: ÁHÁ©Âà  Âan identifier of the call to which the Retrieve Confirmation applies;ÆÆ ÁHÁ©Âà  Âan identifier of the channel over which the held call is reconnected.ÆÆ 2.3.2.6Á  Á(Optional) Notification of Retrieval 2.3.2.6.1  Meaning of (Optional) Notification of Retrieval ÁHÁ(Optional) Notification of Retrieval is the information sent from FE2 towards B indicating that the B Channel between FE1 and FE2 has been reconnected. 2.3.2.6.2  Information Content for (Optional) Notification of Retrieval: ÁHÁThe following information is included in the (Optional) Notification of Retrieval: ÁHÁ©Âà  Âan identifier of the call to which the (Optional) Notification of Retrieval applies.ÆÆ 2.4ÁHÁÃÃFunctional Entity ActionsÄÄ ÁHÁ©Âà  Â201 © Perform the holding functionÆÆ ÁHÁ©Âà  Â202 © Perform the retrieve functionÆÆ ÂHH©Âà  Â203 © Perform the reservation functionÆÆ Ð ` Ð Ð € ÐÁHÁ©Âà  Â204 © Perform the reservation management to insure that:ÆÆ ÁHÁÁ  ÁÂX øÂWhen a user (as identified by a terminal, other possibilities for further study) places a call on holdÆÆ Ð Ð ÐÂHHÂÂX  ÂÂX øÂand reservation applies, a B Channel should always be available on that user's interface for the user to retrieve that call from hold; or setup, retrieve, or connect to another call. One B Channel should be kept available for the user as long as the user has (i) one or more calls on hold with reservation and (ii) is not currently connected to any other call. That is, the network should not reserve more than one B Channel for a user, regardless of how a user is defined (as identified by a terminal, other possibilities for further study).ÆÆ ÁHÁ©Âà  Â205 © identify the call at the FE3/FE4 interface that the ÁFH!GÁoptional notifications apply to.ÆÆ 2.5ÁHÁÃÃSDL Diagrams for Functional EntitiesÄÄ ÁHÁThe SDL diagrams for Functional Entities 1, 2, 3 and 4 are shown in four figures (2©4/Q.83, 2©5/Q.83, 2©6/Q.83 and 2©7/Q.83). (pages 36©40 of this document recoup) 2.6ÁHÁÃÃNetwork physical allocation scenariosÄÄ ÁàHIÁÀ À   FE1     FE2     FE3     FE4ƒ ÁàH:ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàH=ÁScenario 1 À À   TE LE LE TE ƒ ÁàHOÁÀ À                              ƒ ÁàH<ÁScenario 2 À À   TE NT2 NT2 TE ƒ ÁàHOÁÀ À                              ƒ ÁàH<ÁScenario 3 À À   TE LE NT2 TE ƒ ÁàHOÁÀ À                              ƒ ÁàH?ÁScenario 4 À À   TE NT2     LE TE ƒ 3.ÁHÁÃÃCompletion of call to busy subscriberÄÄ ÁHÁUnder study. ÁàHEÁ ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ  ƒ