1、CEPT T/CS*49-04*E 23264/4 0004894 9 (3 T/CS49-04 Page 1 E Recommendation T/CS 49-04 (Vienna 1982, revised in Montpellier 1984) SYSTEM L1 MULTIFREQUENCY PUSH-BUTTON INTERREGISTER SIGNALLING Recommendation proposed by Working Group T/WG 1 1 “Switching and Signalling” (CS) Revised text of the Recommend
2、ation adopted by the “Telecommunications” Commission: “The European Conference of Postal and Telecommunications Administrations, considering - that multifrequency push-button (MFPB) subscribers line signalling may enable faster call setup than decadic - that MFPB signalling provides more codes than
3、decadic pulse signalling; that MFPB signalling employs in-band signals making possible end-to-end interregister signalling between private that, as a system that is also used for simple data communication, MFPB signalling is suitable for a dialogue-like that MFPB telephones are being used more and m
4、ore on extension lines; - that equipment located on the subscribers premises and used for private networks may be based on MFPB pulse signalling; automatic branch exchanges (PABXs); interchange of signalling information; signalling techniques, recommends that members, in conditions favouring M FPB s
5、ignalling over links between analogue transmission interfaces of PABXs located in different countries, use System L1 multifrequency push-button interregister signalling as specified below.” I. 1.1. 1.2. 1.2.1. 1.2.2. 1.2.3. 1.2.4. 1.3. 1.3.1. GENERAL Line signalling System L1 MFPB interregister sign
6、alling is used in conjunction with system L1 line signalling according to Recommendation T/CS 49-01 i. The individual line signals to be provided and their uses are specified in Recommendations T/CS 49-05 2 and T/CS 49-06 3 on System L1 MFPB call control signalling procedures. Principles and field o
7、f application MFPB interregister signalling is suitable for automatic and semi-automatic working between PABXs via terrestrial circuits. System L1 MFPB interregister signalling may be used to setup multi-link-tandem connections. Depending on the signalling procedures concerned, link-by-link or end-t
8、o-end signalling applies. In the case of link-by-link working, the signals, in accordance with CCITT Recommendation 4.25 4, are contained within the appropriate link and are not allowed to spillover into subsequent or preceding links. The maximum number of tandem connections over which a call may be
9、 setup is determined by the type of interconnecting circuits and is subject to mutual agreement between the parties concerned. All circuits used in a tandem connection should be according to the standard of CCITT Recommendations G.171 5 and M.lO1O to M.1060 6. On international leased lines, System L
10、1 MFPB is used on four-wire circuits and the PABX termination arrangements setout in Recommendation T/CS 49-01 I apply. Special arrangements enable System L1 to be used on (national) two-wire circuits, if necessary. Structure The System LI MFPB signalling provides the signalling capability for the i
11、nterchange of additional information during a dialogue phase following the selection phase. During the dialogue phase, the full range of MFPB codes in the forward as well as in the backward direction is used. In this case, the System is called System LI MFPB bidirectional. It is suitable for the imp
12、lementation of an increased range of services. The signalling procedures are specified in Recommendation T/CS 49-06 3. Edition of May 15, 1986 CEPT T/CS*49-04*E = 2326414 0004895 O TICS 49-04 E Page 2 1.3.2. 1.3.3. 2. 2.1. 2.2. 2.3. 2.3.1. 2.3.2. System L1 MFPB signalling is designed, however, to al
13、low the use of a simplified subsystem, called System LI MFPB unidirectional. It provides the signalling capability for call establishment (selection phase) using the character set of the 12-button array according to Recommendation T/CS 46-02 7 in the forward direction only. The signalling procedures
14、 are specified in Recommendation T/CS 49-05 2. A signalling compatibility check is included in the System LI MFPB bidirectional signalling to enable interworking with System L1 MFPB unidirectional. INTERREGISTER SIGNALS Use of line signalling frequency signals In System L 1 MFPB, five line-signallin
15、g-frequency-backward signals are used for interregister type signal- ling, the proceed-to-send signal, the proceed-to-send-on-recall signal, the address-complete signal, the clear-request signal and the reconnect signal. The five signals are introduced in the system as specified in Recommendation T/
16、CS 49-02 SI. Signal codes Table 1 (T/CS 49-04) shows the MFPB forward signals used in System L1 signalling. Table 2 (T/CS 49-04) shows the MFPB backward signals, which occur only in the dialogue phase, e.g. in bidirectional MFPB signalling. The multifrequency codes used are in accordance with Recomm
17、endation T/CS 46-02 7 ; they are designated by the characters 1, 2, 3, 4, 5, 6, 7, 8, 9, O, *, #, A, B, C, and D allocated as specified therein. All signal names are in accordance with Recommendation T/CS 41-01 9. Signals having the same coding shall be distinguished by their position in the sequenc
18、e of the signalling procedure. The range of transmitted signalling information may in certain cases be extended by the use of the escape signal indicating the change-over to another set of meanings valid only for the following signal, or be reduced by the end-ofblock signal indicating that no more s
19、ignals will be transmitted. Signalling sequence System L1 MFPB signalling begins with the transmission of address signals (routing digits and extension number) which are sent character-by-character in a non-compelled mode in the sequence required by the numbering arrangements. This phase, called sel
20、ection phase, may be followed by an additional information interchange, making up the dialogue phase. By means of the register-recall procedure, further MFPB signalling is possible after completion of the call Set-up (see Section 3.). Selection phase The address signals are coded in accordance with
21、Recommendation T/CS 46-02 7 and comprise the characters 1, 2, 3, 4, 5, 6, 7, 8, 9, O, * and #. In transit working, the signals are transmitted link-by-link. Under normal conditions, the selection phase is terminated with the transmission of an address-complete signal. In the simplified subsystem (MF
22、PB unidirectional), this signal also concludes the multifrequency set-up signalling. However, register-recall signalling may follow (see Section 3.). Dialogue phase In the System L 1 MFPB bidirectional signalling, multifrequency signalling continues after the selection phase with forward and backwar
23、d signals as described in Sections 2.4. and 2.5. The dialogue phase signals are transmitted en-bloc in a non-compelled mode, exception being made for the first forward signal, see $2.3.3. Under normal conditions, the dialogue phase is terminated non-compelled by the transmission of the dialogue phas
24、e end-of-block signals in both directions. In transit working, the dialogue phase signals are transmitted end-to-end. Edition of May 15. 1986 CEPT T/CS*49-04*E 2326414 0004896 2 dialogue phase forward signal PSTN call Operator assisting extension Operator assisting PSTN call PSTN access, data protec
25、ted, group b PSTN restr., not data protected, group a PSTN restr., not data protected, group b TICS 49-04 E Page 3 O O Character indicating the MFPB code used t Dialogue phase forward signals Note I Type of call (TC) Class of service of calling party (CSA) Note 3 Note 4 Addr. Sig na1 in the selectio
26、n phase Digit i Note 2 I Extension originated 1 PSTN access, not data protected, group a I Enquiry call, PSTN call held I PSTN access, not data protected, group b Digit 2 Digit 3 PSTN access, not data protected, group a; intrusion privileged Transfer from night extension l3 I Digit 4 1 Data PSTN acc
27、ess, data protected, group b; intrusion privileged l4 Digit 5 l5 Digit 6 16 Digit 7 Digit 8 I Digit 9 PSTN restr., data protected, group a Extension via restricted signalling link l9 Io Digit O I Enquiry call, extension call held I PSTN restr., data protected, group b * I Reserved for end-of-block I
28、 Reserved for end-of-block Operator assisting restr. signalling link Incoming calls barred No restrictions Fully restricted Spares Spares Diverted Network orig. Operator, not assisting a call I IC 3p. The reason for call-refusal may be transmitted after the call-refusal signal. Note 4: A state-of-de
29、stination signal may follow the class-of-service or the called-party-line-identification. Note 5: An escape set is at present being considered for class-of-service signals only (see paragraph 2.5.1.). Signalling compatibility check The first MFPB dialogue phase forward signal, see Table 1 (T/CS 49-0
30、4), requires as a response a first MFPB dialogue phase backward signal, see Table 2 (T/CS 49-04), before forward signalling continues. If that MFPB backward signal has not been recognised within 200 ms, the outgoing PABX shall assume that the dialogue phase is not possible. Dialogue phase forward si
31、gnals The descriptions for the dialogue phase forward signals listed below are set-out in the sequence in which the signals will be transmitted to the destination PABX. See also paragraph 2.4.4. Type-of call signals Two type-of-call signals are used and transmitted one after the other. In principle,
32、 both signals can be freely combined. However, not all combinations are reasonable, e.g. an operator-assisted call will not be network originated. Class-of-ser vice signals A set of fourteen calling party class-of-service signals is given in Table 1 (T/CS 49-04). Other class-of-service indications a
33、re possible by the transmission of the escape signal followed by a signal from Table 3 (T/CS 49-04). Edition of May 15, 1986 CEPT T/CS*49-04*E W 2326434 0004898 b W a 2.4.3. 2.4.4. 2.4.5. 2.5. 2.5.1. 2.5.2. MFPB 1 2 3 4 5 6 7 8 9 O A B C # TICC 49-04 E Page 5 Signal These signals are not yet allocat
34、ed Table 3 (49-04). Allocation of class-of-service of the calling party signals to MFPB codes. If a transit switch indicates with a restricted-signalling-capability signal that the originating PABX is connected over a link with restricted signalling capability, the class-of-service signal will not b
35、e transmitted. Calling-line-iden tity signals The calling-line-identity is transferred from the outgoing PABX to the incoming PABX after the class-of- service information. If a transit switch indicates with a restricted-signalling-capability signal that the originating PABX is connected over a link
36、with restricted signalling capability, the calling-line-identification procedure is omitted. The calling-line-identity signals are the numerical characters of the MFPB code (see Table 1 (T/CS 49-04), Note I). End-of-block signal The end-of-block signal terminates the dialogue phase forward en-bloc s
37、ignal sequence. Forward escape signal The escape signal is at present envisaged for extension of the range of class-of-service signals only. Dialogue phase backward signals The sequence of dialogue phase backward signals depends on whether or not the call offered to the incoming PABX can be accepted
38、. If the call is accepted, the first backward signal, a called party class-of-service signal, will indicate this. Called-line-identification and state-of-destination information may follow. If the call is not accepted, the first MFPB backward signal will be the call-refusal signal and further signal
39、s may follow, indicating the reason for the refusal. Class-of-service signals A set of fourteen called party class-of-service signals is given in Table 2 (T/CS 49-04). The number of class-of-service indications can be extended by the transmission of the escape signal followed by a signal from Table
40、3 (T/CS 49-04). For a PABX each extension is characterised by a class-of-service indication. The same class-of-service applies irrespective of whether the call is outgoing or incoming to the extension. Consequently, the class-of-service signals given in Tables 1 (T/CS 49-04) and 2 (T/CS 49-04) are i
41、dentical. Table 3 (T/CS 49-04), including the note, applies also for backward signalling. If a transit switch indicates with a restricted-signalling-capability signal that the destination PABX is connected over a link with restricted signalling capability, the class-of-service signal will not be tra
42、nsmitted. Reason for refusal After transmission of the call-refusal signal, detailed reasons or advice to be taken by the outgoing PABX may be transferred by the next backward signal. Edition of May 15. 1986 CEPT T/CS*q9-04*E 232b4l14 0004899 8 I T/CS 49-04 E Page 6 2.5.3. 2.5.4. 2.5.5. 2.5.6. 3. 4.
43、 4.1. 4.2. Called-party S-line-identcation The called-partys-line-identity will only be indicated by the incoming PABX if it differs from the address as it has been transmitted during the selection phase, e.g. under all conditions where call diversion has taken place at the destination PABX. This in
44、formation can, however, not be provided if the destination PABX is reached via a link of restricted signalling capability. Called-partys-line-identification may be transmitted in both cases, either when the call is accepted or when the call is refused by the incoming PABX. The called-partys-line-ide
45、ntity signals are the numerical characters of the MFPB code (see Table 2 (T/CS 49-04), Note I). State-of-destination signals The state-of-destination signal indicates the current state of the destination actually reached. If this state changes, a different state-of-destination signal may then be tra
46、nsmitted. End-of-block signal The end-of-block signal terminates the dialogue phase backward signalling sequence. Backward escape signal The escape signal is at present envisaged for extension of the range of class-of-service signals only. REGISTER-RECALL SIGNALLING Register-recall provides the mean
47、s for control information transfer after dismissal of common-control equipment. Register-recall can, as forward or backward recall, be initiated in either direction, regardless of the direction of the original call Set-up. When the common-control equipment at the destination or originating PABX is r
48、equired to be recalled, the forward or backward service-request-recall signal shall be sent. The service-request-recall signal shall not recall the common-control equipment of transit switches. However, certain call states may require response by a transit switch on recognition of a service-request-
49、recall signal, e.g. in a three-party call where branching occurs at a transit switch. In the case of MFPB unidirectional, the proceed-to-send-on-recall signal using the line signalling frequency and specified in Recommendation T/CS 49-02 7 shall be used. In the case of MFPB bidirectional, the proceed-to-send-on-recall signal is coded as the character *. The initiating PABX will continue with the signalling capability check. Register-recall signalling depends on the supplementary services it is used for. When the common-control equipment of a transit swi
