ÿWPCL ûÿ2BJ|xÐ ` ÐÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿH øÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÐ °°°è ÐÑ Âx„|ü@Ž ÑÐ Å@8Ø'@8Ø'Å ÐÓÓÃÃRecommendation Q.50ÄÄ Áà"ÁSIGNALLING BETWEEN CIRCUIT MULTIPLICATION EQUIPMENTS (CME) ANDƒ Áà/ÁINTERNATIONAL SWITCHING CENTRES (ISC)ƒ 1.ÂXHÂÃÃIntroductionÄÄÆÆ Ð ° ÐÁHÁThis Recommendation contains principles and examples of signalling between ISC (exchanges) and their associated circuit multiplication equipments. ÁHÁCircuit multiplication equipments may have integral echo control and A/ÀÀ law converter functions. The information in this Recommendation is compatible with the control procedures for such devices. 2.ÂXHÂÃÃDefinitions relating to CMEÄÄÆÆ ÁHÁFor a complete description of additional definitions see Recommendation Q.dcme. 2.1ÂàHÂÃÃDigital circuit multiplication equipment (DCME) and CMEÄÄÆÆ ÁHÁDCME and CME constitute a general class of equipment which permits concentration of a number of trunks on a reduced number of transmission channels. DCME in particular permits concentration of a number of 64 kbit/s PCM encoded trunks on a reduced number of digital transmission channels. 2.2ÂàHÂÃÃSpeech interpolation; digital speech interpolation (DSI)ÄÄÆÆ ÁHÁA method of profiting from the time instants when a speaker is not active, which is indicated by a speech detector. The channel is then used by another active connection. The signals carried by a transmission channel therefore represent interleaved bursts of speech signals derived from a number of different trunks. 2.3ÂàHÂÃÃLow rate encoding (LRE)ÄÄÆÆ ÁHÁSpeech coding methods with bit rates less than 64 kbit/s, e.g. the 32 kbit/s transcoding process defined in G.721 applied to speech coded according to G.711. 2.4ÂàHÂÃÃSpeech activityÄÄÆÆ ÁHÁThe ratio of the time speech and corresponding hangover occupies the trunk to the total measuring time, averaged over the total number of trunks carrying speech. 2.5ÂàHÂÃÃCME gainÄÄÆÆ Ð H ÐÁHÁThe trunk channel to transmission channel multiplication ratio, which is achieved through application of CME, including LRE and/or speech interpolation (DSI). ÁàHHÁFIGURE 1/Q.50ƒ ÁàHNÁƒ ÁàHJÁÃÃCME gainÄă 2.6ÂàHÂÃÃTrunkÄÄÆÆ ÁHÁA bidirectional connection consisting of a forward channel and a backward channel between the ISC and CME not subject to LRE or DSI operation. 2.7ÂàHÂÃÃTransmission channel © bearer channelÄÄÆÆ ÁHÁOne channel of the connection between the transmit unit and receive unit of corresponding CME. 2.8ÂàHÂÃÃFreeze©outÄÄÆÆ ÁHÁThe temporary condition when a trunk channel becomes active and cannot immediately be assigned to a transmission channel, due to lack of available transmission capacity. 2.9ÂàHÂÃÃFreeze©out fractionÄÄÆÆ ÁHÁThe ratio of the sum of the individual channel freeze©outs to the sum of the active signals and their corresponding hangover times and front end delays, for all trunk channels over a fixed interval of time, e.g. one minute. 2.10ÂhHÂÃÃTransmission overloadÄÄÆÆ ÁHÁThe condition when the freeze©out fraction or average bits per sample goes beyond the value set in accordance with speech quality requirements. 2.11ÂhHÂÃÃOperating modesÄÄÆÆ ÂHHÂÁ€Á2.11.1Á  ÁÃÃPoint©to©point modeÄÄ (see Figures 2a/Q.50 and 2b/Q.50)ÆÆ ÁHÁPoint©to©point © Using Figure 2a/Q.50 for reference, the transmit side CME concentrates N trunks into N/G transmission channels, where G is the CME gain. ÁHÁAt the receive side, the receiving CME simply reconstitutes the N trunks from the N/G transmission channels. ÁàHGÁFIGURE 2a/Q.50ƒ ÁàHNÁƒÔ w.ÔŒÁàH@ÁÃÃPoint©to©point unidirectionalÄă ÁàHGÁFIGURE 2b/Q.50ƒ ÁàHNÁƒ ÁàH:ÁÃÃPoint©to©point two origins unidirectionalÄă ÁàHHÁFIGURE 2/Q.50ƒ ÁàHNÁƒ ÁàH.ÁÃÃMulti©clique for two origins and two destinations unidirectionalÄă ÁàHNÁƒ ÁHÁThe example in Figure 2b/Q.50 also shows a point©to©point mode. From the switching point of view there could be a difference between the configurations in Figures 2a/Q.50 and 2b/Q.50. ÁHÁFor transmission of alarms it has also to be considered, that different exchanges may be connected to one CME. ÂHHÂÁ€Á2.11.2Á  ÁÃÃMulti©clique modeÄÄ (see Figure 3/Q.50)ÆÆ ÁHÁMulti©clique mode © in this mode the pool of transmission channels is sub©divided into several independent pools (cliques) of fixed capacity, each destination specific. If a part of the cliques capacity is not used, it cannot be used for another destination. ÁàHHÁFIGURE 3/Q.50ƒ ÁàHNÁƒ ÁàH8ÁÃÃMulti©clique mode (only one direction shown)Äă ÁàHNÁƒ ÂHHÂÁ€Á2.11.3Á  ÁÃÃMulti©destination modeÄÄÆÆ ÁHÁA DCME operational mode where input trunk channel traffic is interpolated over a pool of available transmission channels for all destinations having traffic in the pool. The transmit trunk channels are designated to receive trunk channels at corresponding locations. ÁHÁFigure 4/Q.50 shows a unidirectional system block diagram for a multi© destination mode with two transmit and two receive DCME units. Ô w.ÔŒÁàHHÁFIGURE 4/Q.50ƒ ÁàHNÁƒ ÁàH6ÁÃÃMulti©destination mode (only one direction shown)Äă 3.ÂXHÂÃÃRequirements for controlÄÄÆÆ 3.1ÂàHÂÃÃReasons for use of circuit multiplication equipments (CME)ÄÄÆÆ ÁHÁCircuit multiplication equipments are used in order to reduce the Ð h Ðbandwith required for transmission of a given set of calls. This can be achieved by reducing the redundancy which is inherent in speech communications. CME gains of up to 5:1 can be achieved using DSI + LRE with subjectively acceptable quality. Thus, the amount of line plant required between switching points and hence the cost of provision can be minimized. 3.2ÂàHÂÃÃIntegration of CMEs into the telephone networkÄÄÆÆ ÁHÁNormally, when an exchange needs an outgoing circuit, the circuit selection is based on circuit availability. In this example, the call may be blocked if all of the circuits are unavailable due to traffic or maintenance. If the same call encounters a CME, the possible outcomes are more complex. ÁHÁFrom the point of view of call set©up, two CME aspects may necessitate information transfer between the exchange and the CME. ÁHÁa)Á   ÁTransmission Capacity © The circuit multiplication characteristics of a CME result in a lower total transmission capacity for the CME as compared to the transmission capacity of all of the input trunks. A call may find a free (unseized) circuit from the exchange to the CME but no available transmission channels between two CMEs. For systems employing speech interpolation, allowing additional calls could lead to unacceptable speech quality degradation due to freeze©out. The probability of freeze©out can be reduced by the creation of overload channels using bit©stealing techniques. Additional quality control is achieved if the exchange knows, through a Transmission Resource Management System, if the CME has available capacity to complete a new call. ÁHÁb)Á   ÁCall Set©Up/Release © Depending on the bearer service type of the call to be set©up, and on whether or not the CME is able by itself to establish the inter©CME connections, the seizing/releasing actions in the exchange may need to be extended to the CME by means of out©of©band information transfer. For example, in DSI systems, speech connections are made dynamically on detection of channel activity performed by built©in speech detectors. For 64 kbit/s unrestricted on©demand connections (and for 3.1 kHz audio, if appropriate) through DSI systems (i.e., not through internal pre©assignment), the establishment and disestablishment of connections between the CMEs have to be initiated from the outgoing exchange. ÁHÁIn general, these two aspects are strictly independent from each other as each serves a different purpose. However, depending on the design criteria in the CME and the call set©up procedures in the exchange and the CME associated with one aspect may be related to that of the other. 3.3ÂàHÂÃÃFactors for signalling functions determinationÄÄÆÆ ÁHÁThe functional requirements for signalling between CMEs and exchanges are determined by the type of CME with its capabilities and limitations, and by the types of bearer services it supports. ÁHÁThe remote control of echo control devices and A/ÀÀ©law converters, if they are integrated into the CME, is accomplished either by the terminal or test equipment or directly from the ISC (based on call set up information/signalling information). ÁHÁRequirements and actions for control of ECD are described in CCITT Recommendation Q.115. 3.3.1ÂðHÂÃÃCircuit multiplication equipment and physical locationÄÄÆÆ ÁHÁThere are different types of CME which are being used or will most likely be used in the international telephone network, each with its own capabilities and limitations: ÂHHÂa)Âh   Â32 kbit/s low rate encoding (LRE);ÆÆ Ð ` Ð ÂHHÂb)Âh   Âanalogue speech interpolation equipment;ÆÆ Ð p ÐÂHHÂc)Âh   Âdigital speech interpolation (DSI) with 64 kbit/s PCM;ÆÆ Ð ` Ð ÂHHÂd)Âh   Âcombined 32 kbit/s LRE and DSIÆÆ ÂHHÂe)Âh   Â16 kbit/s LRE.ÆÆ Ð  ÐÁHÁThe location of certain types of CME relative to the exchange determines the choice of signalling interface. These CMEs can be located at the ISC or remote from the ISC (e.g., at an earth station). Certain types of signalling interfaces may be more practical when these CMEs are co©located with the ISC, and others may be more practical when they are remote from the ISC. Therefore, the location of the CME needs to be considered when choosing the signalling between ISC and CME. Ð H ÐÁHÁWhen the CME is remote from the ISC, the link between the ISC and CME could be composed of digital or analogue transmission path. Both conditions have different equipment configurations and different signalling requirements (see section 7). 3.3.2ÂðHÂÃÃBearer services supported on CME linksÄÄÆÆ ÁHÁUp to four basic bearer service types are supported or will likely be supported by CMEs in the international network: Ð  ÐÂHH©Âà  Âspeech bearer service (full duplex, analogue or digital);ÆÆ Ð ` Ð ÂHH©Âà  Â3.1 kHz audio bearer service (full duplex);ÆÆ ÂHH©Âà  Â64 kbit/s unrestricted bearer service (full duplex);ÆÆ Ð ( ÐÂHH©Âà  Âalternate speech/64 kbit/s unrestricted bearer service (full duplex) (in call modification is for further study).ÆÆ Ð ` Ð Ð X ÐÁHÁEach CME type supports one or more bearer services depending on special facilities or functional options built in the equipment. ÁHÁDifferent LRE algorithms will also have different levels of performance, for instance, in terms of voiceband data. Since certain speech optimized algorithms have limited transparency to voice band data, the CME has internal facilities (e.g., data detectors combined with route around mechanisms and/or special algorithms) to overcome its inherent limitations. This approach clearly separates the CME transmission problems from the ISC switching functions as much as possible to allow independent developments. ÁàÀJÁTABLE 1/Q.50ƒ ÁàÀPÁƒ ÁàÀ,ÁÃÃBearer services supported in CMEs in relation to CME©exchange signallingÄă Ô w.ÔŒ List of abbreviations: TRM = transmission resource management CSM = call set©up messages between CME and ISC NS = bearer service not supported NX = bearer service supported without message exchange FS = further study 1)    message exchange not necessarily implemented 2)    supported through pre©assignments (e.g., Recommendation G.761       transcoder DNI) 3)    supported in a limited fashion (e.g., Recommendation G.761) 4)    CSM not needed with internal CME special handling facilities 4.ÂXHÂÃÃBearer services and CME techniques in the context of signallingÄÄÆÆ ÁHÁTable 1/Q.50 gives the relationship between CME techniques and the four bearer services identified in ÀÀ 3.3.2 with regard to their supportability and the need for CME©exchange message transfer. ÁHÁThe signalling function requirements are categorized on the basis of bearer services supported by the different CME techniques. For speech bearer services, transmission resource management (TRM) information alone is adequate especially for CMEs employing speech interpolation. The objective of this provision is to maintain the reduction of transmission quality within tolerable limits. In addition to TRM information, external call set©up message (CSM) exchange is needed for bearer services involving on©demand 64 kbit/s unrestricted service in contemporary digital circuit multiplication equipment (32 kbit/s LRE and DSI). 5.ÂXHÂÃÃDivision of functionality between the ISC and the CMEÄÄÆÆ 5.1ÂàHÂÃÃCME dynamic load control processÄÄÆÆ ÁHÁTransmission resource management (TRM) information is based on traffic load measurements at the local and distant CMEs. Therefore in the multi© destination and multi©clique mode of operation, TRM information is provided for each destination/clique separately. ÁHÁA universal arrangement is used for handling TRM information between CME and an ISC. The TRM information is dynamically presented to the exchange in one of two states for each bearer service. The states are called "available" and "not available". Logic within the CME is used to determine which of the two states should be indicated to the exchange regardless of any condition at the exchange. ÁHÁWhen a CME encounters a "not available" state for a bearer service (either locally or remotely), it presents this indication to the exchange so it will stop routing new calls to the CME for that bearer service even if there are free, unseized circuits available. The exchange will continue to prohibit calls to the CME until it receives an "available" indication for the bearer service when in both, local and remote CMEs, there is no overload. ÁHÁThis dynamic load control information is therefore directly influencing the circuit selection process in the exchange during call set©up for each bearer service separately. The circuit selection in the exchange is a check whether or not a free unseized circuit is suitable for a certain bearer service type, for which a new call is to be accommodated. For example, the exchange would select a free circuit for a speech call if "speech capacity available" is indicated, irrespective of the indications for other bearer service types. If the DCME link is unable to accommodate additional new 64 kbit/s calls, all free unseized circuits within the exchange will be marked accordingly. Even though the generation of bearer service related TRM information with DCMEs may be in part mutually dependent (i.e., no capacity for speech implies no capacity for any other bearer service types but not necessarily vice©versa), separate signalling and processing for each bearer service type are necessary to allow different future CMEs to develop independently. 5.2ÂàHÂÃÃCall set©up processÄÄÆÆ ÁHÁAccording to Table 1/Q.50, the contemporary digital circuit multiplication equipment, having the capability to support on©demand all four identified bearer services, in addition to providing TRM to the exchange, requires call set©up messages (CSM) (from the exchange) for selecting bearer services. ÁHÁFor the 64 kbit/s unrestricted bearer service, a circuit is selected if "unrestricted capacity available" is indicated, and a CSM in the form of Seizure/Select request is forwarded to the DCME. An acknowledgement (positive or negative) is sent upon recognition of a 64 kbit/s request even if capacity is available. ÁHÁThe positive acknowledgement can be used by the ISC to initiate the interexchange signalling to the next ISC (e.g. transmission of the IAM of Signalling System No. 7). A failure to establish a 64 kbit/s circuit between CMEs must be reported to the ISC as soon as the condition has been identified by the CME by using an out©of©service message. ÁHÁThe out©of©service message is considered by the ISC to be equivalent to the alarm signal defined in Recommendation Q.33. The ISC will take release actions (if appropriate) as specified in Recommendation Q.33, ÀÀ 4. ÁHÁThe released 64 kbit/s message from the ISC will be positively acknowledged after proper completion of the DCME circuit disestablishment process. Failure to complete this process shall be notified to the ISC using an ÃÃout©of©serviceÄÄ message and the DCME will put the circuit in a blocked condition. After the failure condition is removed, this circuit will be in idle condition and a ÃÃback©in©serviceÄÄ message shall be sent to the ISC. ÁHÁUnder a 64 kbit/s unrestricted dual seizure situation, the non© controlling ISC will initiate a release of the DCME connection using procedures defined in the appropriate inter ISC signalling system protocol. If the DCME is unable to re©establish a remotely released 64 kbit/s duplex connection, it shall indicate this abnormal situation to the appropriate ISC by an out©of© service message. ÁHÁThe information elements and procedures necessary to support the alternate 64 kbit/s speech bearer services are for further study.Ô w.ÔŒ ÁàÀJÁFIGURE 5/Q.50ƒ ÁàÀPÁƒ ÁàÀ@ÁÃÃTypical ISC/CME information flowsÄă ÁàÀPÁƒ 5.3ÂàHÂÃÃInter©dependency between dynamic load control and call set©up processÄÄÆÆ ÁHÁTo allow a standard method of interworking with inter©exchange signalling systems it is important to adopt the functional interdependency between TRM and CSM as described above. 6.ÂXHÂÃÃControl information elements between ISC and CMEÄÄÆÆ ÁHÁThe amount of control information elements utilized between the ISC and the CME depends on the capabilities of the CME and the ISC. Two categories of CME signalling capabilities are recognized. The first category of CME (Type 1) is capable of only transmitting signals from the CME to the ISC (e.g. Dynamic Load Control, see paragraph 6.1). The second category of CME (Type 2) is able to transmit and receive signals to/from the ISC. Tables 2/Q.50, 3/Q.50 and 4/Q.50 give a set of information elements and their flow on the control link between the ISC and the CME for the second category of CME. 6.1ÂàHÂÃÃInformation elements for Type 1 CMEÄÄÆÆ ÁHÁType 1 CME only should use the following types of information elements. The "m" indicates mandatory use, the "o" optional use. ÁHÁ1. Á   ÁNo capacity for speech available (m) ÁHÁ2. Á   ÁChannel(s) available for speech (m)  ÁHÁÁ  Á(speech includes 3.1 kHz audio) ÁHÁ3. Á   ÁOut©of©service (o) ÁHÁ4. Á   ÁBack©in©service (o) 6.2ÁHÁÃÃInformation elements for Type 2 CMEÄÄ ÁàÀJÁTABLE 2/Q.50ƒ ÁàÀ4ÁÃÃInformation elements for transmission resource managementÄă ÁàÀ>ÁÃÃ(load control) CME/ISC (Type 2)ÄÄ ƒ ÁàÀ2ÁÀ ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Àƒ ÁàÀ<ÁÀ ÀType of informationÀ À        Notes             À ÀDirection ofÀ Àƒ ÁàÀDÁÀ À element (Note a)  À À                          À À   the      À Àƒ ÁàÀHÁÀ À                   À À                          À Àinformation À Àƒ ÁàÀJÁÀ À                   À À                          À À  element   À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ8ÁÀ À1.1 No capacity    À À No bearer capacity       À À CME©©>ISC À Àƒ ÁàÀ6ÁÀ Àm   for speech     À À for additional trunk(s) À À À Àƒ ÁàÀ7ÁÀ À    available      À À available À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ6ÁÀ À1.2 Trunk(s)      À À This information element À À CME©©>ISC À Àƒ ÁàÀ5ÁÀ Àm   available for  À À is sent to notify the À À À Àƒ ÁàÀ9ÁÀ À    speech         À À end of "No capacity for À À À Àƒ ÁàÀ<ÁÀ À                   À À speech available" À À À Àƒ ÁàÀ<ÁÀ À                   À À condition À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ6ÁÀ À1.3 No trunk(s)    À À No bearer capacity for   À À CME©©>ISC À Àƒ ÁàÀ3ÁÀ Ào available for  À À additional 3.1 kHz audio À À À Àƒ ÁàÀ5ÁÀ À    3.1 kHz audio  À À trunk(s) available À À À Àƒ ÁàÀ4ÁÀ À    Note 1 À À À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ7ÁÀ À1.4 Trunk(s)       À À This information element À À CME©©>ISC À Àƒ ÁàÀ5ÁÀ Ào   available for  À À is sent to notify the À À À Àƒ ÁàÀ8ÁÀ À    3.1 KHz        À À end of "No trunk À À À Àƒ ÁàÀ8ÁÀ À   Note 1         À À available for 3.1 kHz À À À Àƒ ÁàÀ<ÁÀ À                   À À audio" condition À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ6ÁÀ À1.5 No 64 kbit/s   À À No bearer capacity for   À À CME©©>ISC À Àƒ ÁàÀ7ÁÀ Àm   capacity       À À additional 64 kbit/s À À À Àƒ ÁàÀ7ÁÀ À    available      À À trunk(s) available À À À Àƒ ÁàÀ2ÁÀ À Note 2 À À À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ?ÁÀ À1.6 AcknowledgementÀ À                          À À ISC©©>CME À Àƒ ÁàÀ3ÁÀ Ào   of À À À À À Àƒ ÁàÀ4ÁÀ À    "No 64 kbit/s À À À À À Àƒ ÁàÀ4ÁÀ À    capacity À À À À À Àƒ À À available À À À À À À ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ ÁàÀ6ÁÀ À1.7 Trunk(s)       À À This information element À À CME©©>ISC À Àƒ ÁàÀ5ÁÀ Àm   available for  À À is sent to notify the endÀ À À Àƒ ÁàÀ7ÁÀ À    64 kbit/s      À À of "No 64 kbit/s capacityÀ À À Àƒ ÁàÀ<ÁÀ À                   À À available" overload À À À Àƒ ÁàÀ<ÁÀ À                   À À condition À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ?ÁÀ À1.8 AcknowledgementÀ À                          À À ISC©©>CME À Àƒ ÁàÀ3ÁÀ Ào   of trunk(s) À À À À À Àƒ ÁàÀ4ÁÀ À    available for À À À À À Àƒ ÁàÀ4ÁÀ À    64 kbit/s À À À À À Àƒ ÁàÀ2ÁÀ ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Àƒ ÃÃNote aÄÄ © Each information element may be sent as a message or may be implicit by the lack of a signal (e.g. the CME may send a signal for no capacity for speech available and remove the same signal to indicate trunks available for speech). m = mandatory for this type of CME o = optional for this type of CME ÁàÀJÁTABLE 3/Q.50ƒ ÁàÀPÁƒ ÁàÀ3ÁÃÃInformation elements for seizure/release (CME/ISC (Type 2))Äă ÁàÀ2ÁÀ ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Àƒ ÁàÀ;ÁÀ ÀType of information À À       Notes             À ÀDirection ofÀ Àƒ ÁàÀFÁÀ À  elements       À À                         À À   the      À Àƒ ÁàÀHÁÀ À                    À À                         À Àinformation À Àƒ ÁàÀJÁÀ À                    À À                         À À  element   À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ8ÁÀ À2.1  64 kbit/s      À ÀSent when 64 kbit/s      À À ISC©©>CME À Àƒ ÁàÀ8ÁÀ Àm    select/        À Àcircuit is required via À À À Àƒ ÁàÀ8ÁÀ À     seizure        À Àthe DCME (Note 3) À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ;ÁÀ À2.2  Trunk          À ÀExplicit or implicit     À À ISC©©>CME À Àƒ ÁàÀ7ÁÀ Àm    identity       À Àinformation to assign an À À CME©©>ISC À Àƒ ÁàÀ<ÁÀ À                    À Àinformation element to a À À À Àƒ ÁàÀ<ÁÀ À                    À Àspecific trunk À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ4ÁÀ À2.3  64 kbit/s pos. À ÀSent if 64 kbit/s requestÀ À CME©©>ISC À Àƒ ÁàÀ4ÁÀ Àm    Acknowlegement À Àcan be satisfied À À À Àƒ ÁàÀ<ÁÀ À                    À À(Note 4)(Note 5) À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ6ÁÀ À2.4  64 kbit/s  À ÀSent if a 64 kbit/s      À À CME©©>ISC À Àƒ ÁàÀ7ÁÀ Àm    negative       À Àrequest cannot be À À À Àƒ ÁàÀ4ÁÀ À     AcknowledgementÀ Àsatisfied (Note 5) À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ8ÁÀ À2.5  Release        À ÀSent by the originating  À À ISC©©>CME À Àƒ ÁàÀ7ÁÀ Àm    64 kbit/s      À ÀISC to indicate that a À À À Àƒ ÁàÀ<ÁÀ À                    À À64 kbit/s circuit is not À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ2ÁÀ À2.6 Release À ÀSent to indicate À À CME©©>ISC À Àƒ ÁàÀ2ÁÀ Àm 64 kbit/s pos. À Àsuccessful completion of À À À Àƒ ÁàÀ2ÁÀ À AcknowledgementÀ ÀRelease (Note 5) À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ8ÁÀ À2.7  3.1 kHz        À ÀRequest to allocate data À À ISC©©>CME À Àƒ ÁàÀ4ÁÀ Ào    service/select À Àoptimized facilities À À À Àƒ ÁàÀ4ÁÀ À     seizure À À À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ8ÁÀ À2.8  3.1 kHz        À ÀSent if 3.1 kHz service  À À CME©©>ISC À Àƒ ÁàÀ5ÁÀ Ào    service, pos.  À Àrequest can be satisfied À À À Àƒ ÁàÀ4ÁÀ À     AcknowledgementÀ À À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ8ÁÀ À2.9  3.1 kHz        À ÀSent if 3.1 kHz service  À À CME©©>ISC À Àƒ ÁàÀ5ÁÀ Ào    service/    À Àrequest cannot be À À À Àƒ ÁàÀ8ÁÀ À     negative       À Àsatisfied À À À Àƒ À À AcknowledgementÀ À À À À À ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ;ÁÀ À2.10 Release        À ÀSent to indicate         À À ISC©©>CME À Àƒ ÁàÀ8ÁÀ Ào    3.1 kHz        À Àtermination of the call À À À Àƒ ÁàÀ4ÁÀ À     service À À À À À Àƒ ÁàÀ2ÁÀ ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Àƒ ÁàÀ2ÁÀ ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Àƒ ÁàÀ;ÁÀ ÀType of information À À       Notes             À ÀDirection ofÀ Àƒ ÁàÀFÁÀ À  elements       À À                         À À   the      À Àƒ ÁàÀHÁÀ À                    À À                         À Àinformation À Àƒ ÁàÀJÁÀ À                    À À                         À À  element   À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ4ÁÀ À2.11 Speech service À ÀSent to indicate speech  À À ISC©©>CME À Àƒ ÁàÀ4ÁÀ Ào    select/seizure À Àservice request À À À Àƒ ÁàÀ2ÁÀ À (Note 6) À À À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ6ÁÀ À2.12 Speech, pos.   À ÀSent if speech request   À À CME©©>ISC À Àƒ ÁàÀ4ÁÀ Ào    AcknowledgementÀ Àcan be satisfied À À À Àƒ ÁàÀ2ÁÀ À (Note 6) À À À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ4ÁÀ À2.13 Speech negativeÀ ÀSent if speech request   À À CME©©>ISC À Àƒ ÁàÀ4ÁÀ Ào    AcknowledgementÀ Àcannot be satisfied À À À Àƒ ÁàÀ2ÁÀ À (Note 6) À À À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ3ÁÀ À2.14 Release speech À ÀSent to indicate that theÀ À ISC©©>CME À Àƒ ÁàÀ7ÁÀ Ào    (Note 6)       À Àspeech circuit is not À À À Àƒ ÁàÀEÁÀ À                    À Àrequired any longer      À À            À Àƒ ÁàÀ2ÁÀ ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Àƒ ÁàÀJÁTABLE 4/Q.50ƒ ÁàÀPÁƒ ÁàÀ6ÁÃÃInformation elements for maintenance (CME/ISC) Type 2Äă ÁàÀ2ÁÀ ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Àƒ ÁàÀ;ÁÀ ÀType of information À À       Notes             À ÀDirection ofÀ Àƒ ÁàÀFÁÀ À  elements       À À                         À À   the      À Àƒ ÁàÀHÁÀ À                    À À                         À Àinformation À Àƒ ÁàÀJÁÀ À                    À À                         À À  element   À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ6ÁÀ À3.1 Maintenance     À ÀSent for manual control, À À CME©©>ISC À Àƒ ÁàÀ4ÁÀ Ào   Release Signal  À ÀÃÃplannedÄÄ removal from À À À Àƒ ÁàÀ8ÁÀ À    (Note 7)        À Àservice À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ8ÁÀ À3.2 Maintenance     À ÀSent to acknowledge      À À ISC©©>CME À Àƒ ÁàÀ8ÁÀ Ào   Release         À Àreception of Maintenance À À À Àƒ ÁàÀ4ÁÀ À    Acknowledgement À ÀRelease, ISC is waiting À À À Àƒ ÁàÀ8ÁÀ À    (Note 7)        À Àfor the release of the À À À Àƒ ÁàÀ<ÁÀ À                    À Àtrunk À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ7ÁÀ À3.3 CME clear of    À ÀSignal sent when all     À À ISC©©>CME À Àƒ ÁàÀ4ÁÀ Ào   traffic signal  À À(this) trunk(s) are (is) À À À Àƒ ÁàÀ4ÁÀ À    (released after À Àidle. The ISC prevents À À À Àƒ ÁàÀ6ÁÀ À    maintenance     À Ànew seizures on these À À À Àƒ ÁàÀ4ÁÀ À    release signal) À À(this) trunk(s). À À À Àƒ ÁàÀ3ÁÀ À    (Note 7) À À À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ8ÁÀ À3.4 Out©of©service  À ÀGeneral CME trunk        À À CME©©>ISC À Àƒ ÁàÀ;ÁÀ Àm                   À Àunavailable signal used À À À Àƒ ÁàÀ<ÁÀ À                    À Àon a per circuit basis À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ4ÁÀ À3.5 Out©of©service  À ÀSent to acknowledge "Out©À À ISC©©>CME À Àƒ ÁàÀ4ÁÀ Ào   acknowledgement À Àof©service signal" used À À À Àƒ ÁàÀ<ÁÀ À                    À Àon a per circuit basis À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ5ÁÀ À3.6 Back©in©service À ÀSent after the removal   À À CME©©>ISC À Àƒ ÁàÀ7ÁÀ Àm   (Note 7)        À Àfrom service is no À À À ÀƒÔ w.ÔŒÁàÀ<ÁÀ À                    À Àlonger necessary © used À À À Àƒ ÁàÀ<ÁÀ À                    À Àon a per circuit or per À À À Àƒ ÁàÀ<ÁÀ À                    À ÀCME basis À À À Àƒ ÁàÀ2ÁÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀƒ ÁàÀ5ÁÀ À3.7 Acknowledgement À ÀUsed on a per circuit    À À ISC©©>CME À Àƒ ÁàÀ5ÁÀ Ào   of "Back©in©    À Àbasis À À À Àƒ ÁàÀ4ÁÀ À    service" À À À À À Àƒ ÁàÀ2ÁÀ ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Àƒ ÃÃNotes to Table 2/Q.50ÄÄ ÃÃNote 1ÄÄ © This information may be implicit in information element 1.1 (e.g. because 3.1 kHz audio data and speech may be supported by the same LRE algorithm or 3.1 kHz audio data is detected by the CME using inband signals (2 100 Hz) from the data terminal). ÃÃNote 2ÄÄ © If a defined portion of the bearer capacity is used for special call types (definition of minimum and/or maximum number of channels per call type, e.g. for 3.1 kHz audio or 64 kbit/s), a special load control information is needed for each of these call types. ÃÃNotes to Table 3/Q.50ÄÄ ÃÃNote 3ÄÄ © Preassigned digital non©interpolated (DNI) 64 kbit/s channels do not need this information element. ÁHÁA 64 kbit/s select/seizure information element between CME and ISC is mandatory for type 2 CME equipment, if 64 kbit/s channels are used on a demand basis. ÃÃNote 4ÄÄ © Dependent on the realization of the CME there could be a longer or shorter delay for 64 kbit/s channel acknowledgement. ÃÃNote 5ÄÄ © "Mandatory" refers to the presence of these information elements at the signalling interface between ISC and CME. The use of these elements is optional, however these elements are preferred to provide safeguards for proper operation. ÃÃNote 6ÄÄ © The request for speech service may be implicit, that means, that a discrete information flow may not be required. ÁHÁFor indication of termination (not interruption) of a call, select/seizure and release may be necessary on a per call basis. ÃÃNotes to Table 4/Q.50ÄÄ ÃÃNote 7ÄÄ © Information elements 3.1, 3.2, 3.3 and 3.6 are a set of elements that should only be used together. ÁHÁInformation element 3.6 could also be used after "out©of©service" © information without 3.1, 3.2 and 3.3. 7.ÁHÁÃÃTransmission techniques for ISC©CME signallingÄÄ ÁHÁThe selection of a transmission technique (signalling protocol) for transferring CME control information between the CME and the ISC will be determined by each administration and it will be based on numerous factors. ÁHÁSome of the key factors are: ÁHÁ©Á  Álocation of the CME and the ISC(s) ÁHÁ©Á  Átype of facility between the CME and the ISC (e.g. analogue, ÁI°"JÁÁJ(#KÁdigital) ÁHÁ©Á  Áperformance of the signalling link ÁHÁ©Á  Áelectrical interface with the ISC ÁHÁ©Á  Ásoftware capabilities of the ISC ÁHÁ©Á  Áand the complexity of the desired signalling. ÁHÁAll these functions need to be considered when selecting a transmission technique. ÁHÁThe choice of a transmission technique is for further study. 7.1ÁHÁÃÃExternal data pathÄÄ ÁHÁExamples of separate data paths are: ÁHÁ©Á  ÁV 24 interface, ÁHÁ©Á  Ácopper loop 7.2ÁHÁÃÃChannel associated signallingÄÄ ÁHÁExamples of channel associated links are: ÁHÁ©Á  ÁTS 16 of PCM 2 Mbit/s ÁHÁ©Á  Áoutband signalling, e.g., 3 825 Hz ÁHÁ©Á  Áa nominated 64 kbit/s PCM timeslot 7.3ÁHÁÃÃCommon channel signalling in the PCM access streamÄÄ ÁHÁExamples of common channel signalling are: ÁHÁ©Á  Áuse of specialized messages integrated into the common channel ÂHHÂÂX  Âsignalling systems to be interpreted by the CME;ÆÆ Ð ` Ð Ð ( ÐÁHÁ©Âà  Âone dedicated common channel signalling link for exchange of information elements between ISC and CME.ÆÆ 8.ÁHÁÃÃRecommendation for signalling systemÄÄ ÁHÁFor further study. 9.ÁHÁÃÃExample systemsÄÄ ÁHÁTwo example systems can be found in Annexes A and B to this Recommendation.