1、CEPT T/CS*49-01*E = 232b414 00048b8 8 0 TCs49-01 Page E 1 Recommendation T/CS 49-01 (Ostend 1979, revised in Vienna 1982 and Montpellier 1984) SYSTEM L1 LINE SIGNALLING OVER INTERNATIONAL INTER-PRIVATE AUTOMATIC BRANCH EXCHANGE LINES Recommendation proposed by Working Group T/WG 1 1 “Switching and S
2、ignalling” (CS) Text of the Recommendation revised adopted by Commission “Telecommunications” “The European Conference of Postal and Telecommunications Administrations, considering that there is an increasing need for the interconnection of private automatic branch exchanges located in different cou
3、ntries by means of international leased lines; that these international connections between private automatic branch exchanges should permit a fully automatic service between extensions connected to the private automatic branch exchanges conceined and auihorised for international trafic; O - that CC
4、ITT Recommendations Q. 1 i and Q.2 2, since they are not directly applicable to international leased circuits, cannot cover the automatic service either; that a proliferation of private systems designed by suppliers tends to make operation and maintenance more dificult, recommends that the members,
5、when introducing international interconnections over links between analogue transmission interfaces of private automatic branch exchanges, use the System L1 line signalling, which comprises the signals, equipment functions and procedures specified in the following. The requirements refer to the inte
6、rfaces between the link and the outgoing or incoming private automatic branch exchange. The private automatic branch exchanges at both ends are regarded as functional units and no specifications are included on the ways and means for the provision of the functions concerned.” O 1. 1.1. 1.2. 1.3. 1.4
7、. 1.5. 1.6. 1.7. 1 .s. PRINCIPLES AND FIELDS OF APPLICATION The line signalling system is to provide automatic and semi-automatic working between private automatic branch exchanges (PABXs) in different countries, via terrestrial circuits. The use of the system over satellite circuits and over compos
8、ed terrestrial satellite circuits is possible, provided that echo-suppressors or echo-cancellers needed are installed on the customer side between the hybrid and the 2,280 Hz sending and receiving equipment. The signalling system is a single voice,frequency (I vfj tone-on-idle line signalling system
9、 using a signalling frequency of 2,280 Hz. The use of voice frequency signals renders the system suitable for all voice transmission media, except those using speech interpolation. The system is intended for use on both-way inter-PABX circuits. Either decadic pulsing or multifrequency interregister
10、signalling may be used with the system (see Explana- tory notes on Group 49 Recommendations preceding this Recommendation). The provision of particular line signals will depend upon the requirements of the associated interregister signalling system. The system operates on a four-wire basis, forward
11、and backward signals being segregated by utilising the four-wire circuit as two separate signalling paths. The send pair to which signals are applied is the receive pair at the distant end. Figure 1 (T/CS 49-01) shows a termination at one end. In addition to the application or removal of signalling
12、frequency (tone-on and tone-off) in continuous form, the transmission of pulses of signalling frequency is applied. When in the idle condition, the signalling frequency applied to the line is reduced in power level to conform to the transmission loading requirements of CCITT Recommendation Q. 15 3.
13、The line signalling operates on a link-by-link basis and may be used to establish a multi-link tandem connection using one or more private automatic exchange(s) as a transit switch. Im accordance with CCITT Recommendation 4.25 4, the signals are contaned within the appropriate link and are not allow
14、ed to spill over into subsequent or preceding links. Edition of May 15, 1986 CEPT T/CS*4-OL*E = 232b4L4 00048b T T/CC49-01 E Page 2 2280 Hz SENDER7 1 SEND SIGNALLING / PATH PABX TERMINATION PABX I 4 -?NIRE CIRCUIT I y RECEIVE SIGNALLING i PATH PABX TERMINATION 2280 Hr SIGNAL OUTPUT 1.9. 1.10. 2. 3.
15、3.1. 3.2. Figure 1 (T/CS 49-0 1). Four-wire private automatic branch exchange termination. The maximum number of tandem connections over which a call may be set-up is determined by the type of interconnecting circuits and is subject to mutual agreement by the parties concerned. However, all circuits
16、 used in a tandem connection should be to the standard of CCITT Recommendations G.171 5 and M.lO1O to M.1060 6. Forward signals may be passed while speech or audible indications (tones or recorded announcements) are being received in the backward direction. A through speech path shall be provided in
17、 the backward direction of transmission during call Set-up. SYSTEM L1 LINE SIGNALS The names and meanings of the signals specified for System LI line signalling are in accordance with Recommendation T/CS 41-01 7. The following signals may be provided: Seizing signal. - Seizing-acknowledgment/Proceed
18、-to-send signal (see Section 5.2.). - Clear-forward signal. Clear-back signal. - Cleared signal. - Answer signal. - Forward-service-request-recall signal. - Forward-link-recall signal. - Backward-service-request-recall signal. Backward-link-recall signal. - Intrusion signal. - End-of-intrusion signa
19、l. All signals above, except the proceed-to-send signal, are supervisory signals. LINE SENDING AND DETECTING REQUIREMENTS General With the tone-on-idle signalling method, a signalling tone is sent continuously over the transmission channels in both directions when the circuit is idle. The presence o
20、f the tone indicates to both ends that the circuit is available and free to accept calls. This idle line signal condition represents the idle state of the circuit. The tone is removed in the forward direction at the moment of seizure and in the backward direction when the first backward signal needs
21、 to be transferred. Restoring tone in the forward direction creates a total of four line signal conditions. The transition from one line signal condition to another one corresponds to the transfer of a line signal, according to the specifications referred to in Section 2. above. The use of these tra
22、nsitions only, however, does not provide for a sufficient number of signals. Therefore, as a call proceeds, each signal condition on the line may be repeated, and also single and double tone-on pulses may be used. Distinction between different signals having the same characteristics shall be made by
23、 the position of the signal in the sequence of the signalling procedure. Line signai conditions and signalling codes The line signal conditions and the signalling codes shall be as shown in Table 1 (T/CS 49-01). Signal sending and detection requirements are given in Sections 3.3. and 3.4. All signal
24、s sent shall give a true indication of the state the call-handling procedure has reached in the PABX concerned. Edition of May 15, 1986 CEPT T/CS*49-OL*E W 2326434 0004870 b 3.3. 3.3.1. 3.3.2. 3.3.3. 3.3.4. 3.4. TICS 49-01 E Page 3 The provision and use of particular line signals, some of which are
25、optional, will depend upon the requirements of the associated type of inter-register signalling (see Recommendations on System L 1 call control signalling procedures). Sending of signals Tone-on and tone-off conditions referred to in Sections 3.1.-3.3. shall conform to the line signalling transmis-
26、sion requirements set out in Section 4. Signals are sent by applying either a tone-on or a tone-off condition to the send signalling path in a continuous or pulsed form as defined below. Continuous tone-on condition A continuous tone-on condition shall be the application of the signalling frequency
27、to the send signalling path for a period exceeding 300 ms. Continuous tone-off condition A continuous tone-off condition shall exist when any signalling frequency is absent from the send signalling path for a period exceeding 80 ms. Single tone-on pulse signal A single tone-on pulse signal shall be
28、the application of a tone-on condition to the send signalling path for a period of 45 to 135 ms. This signal shall not be sent within 250 ms of a previous tone-on condition in the same direction. Double tone-on pulse signal A double tone-on pulse signal shall be the application of two pulses of tone
29、-on condition to the send signalling path, each persisting for a period of 45-135 ms, separated by a tone-off condition for a period of 30-70 ms. This signal shall not be sent within 250 ms of a previous tone-on condition in the same direction. Signal Idle (pro memoriam) Seizing Seizing-acknowledgem
30、ent or proceed-to-send Answer Clear-forward Clear-back Cleared signal Forward-service-request-recall Backward-service-request-recall Intrusion End-of-intrusion Forward-link-recall Backward-link-rccall Outgoing PABX Continuous tone-on Continuous tone-off - Continuous tone-on Single tone-on pulse Sing
31、le tone-on pulse Single tone-on pulse Double tone-on pulse - Incoming PABX Continuous tone-on Continuous tone-off Single tone-on pulse Continuous tone-on Continuous tone-on Single tone-on pulse - - Double tone-on pulse Legend: indicates that the signal is intended to be received by the PABX referred
32、 to at the top of the column. Table 1 (T/CS 49-01). Line signal conditions and signalling codes. Detection of signals Electrical conditions conforming to the line signal transmission requirements specified in Section 4.2. applied to the PABX termination, shall be regarded as a potential signal. Sign
33、als are received in a continuous or pulsed form, as weither a tone-on or a tone-off line signal condition on the receive signalling path. To discriminate between signals having similar characteristics and between signals and spurious electrical conditions, it is necessary to state the minimum persis
34、tence time for a potential signal. A potential signal is not recognised until the electrical condition proper to the signal (Le. tone-on or tone-off) has persisted for a stated period. Until that period expires, only an electrical condition exists. Paragraphs 3.4.1 .-3.4.4. detail the minimum persis
35、tence of a defined electrical condition before it may be recognised as a signal, i.e. an electrical condition persisting for less than the stated period shall not be recognised as a signal. The period after which a potential signal must be recognised as a signal is a function of the PABX logic and i
36、s not given in these specifications. However, recognition should occur as soon as possible following expiration of the stated persistence check period, and the splitting and spill-over requirements (see Section 4.) must be met. Edition of May 15, 1986 CEPT T/CS*49-01*E 2326434 000487L 8 TICS 49-01 E
37、 Page 4 3.4.1, 3.4.2. 3.4.3. 3.4.4. 4. 4.1. 4.1.1. 4.1.1.1. 4.1.1.2. 4.1.1.3. 4.1.2. Continuous tone-on condition A tone-on condition applied to the receive signalling path PABX termination may be recognised as a continuous tone-on condition for signalling when it has persisted for 150 ms. Continuou
38、s tone-of condition A tone-off condition applied to the receive signalling path PABX termination may be recognised as a continuous tone-off condition for signalling when it has persisted for 40 ms. Single tone-on pulse signal A tone-on condition applied to the receive signalling path PABX terminatio
39、n and persisting for a period of 35-1 50 ms, followed by a tone-off condition of longer than 200 ms, may be recognised as a single tone-on signal. A tone-on condition persisting for less than 25 ms followed by a tone-off condition for less than 80 ms, shall not be recognised as a single tone-on puls
40、e signal. Double tone-on pulse signal Two pulses of tone-on condition applied to the receive signalling path PABX termination, each persisting for a period of 35-150 ms, separated by a tone-off condition for a period of 20-80 ms and followed by tone-off condition for longer than 200 ms, may be recog
41、nised as a double tone-on pulse signal. Two tone-on pulses persisting for less than 25 ms, or separated by a tone-off condition for more than 200 ms, or followed by tone-off condition for less than 80 ms, shall not be recognised as a double tone-on pulse signal. LINE SIGNALLING TRANSMISSION REQUIREM
42、ENTS Signal sender Signals are sent by the application of a tone-on condition or a tone-off condition or a combination of both to the transmit signalling path. Tone-on condition Tone-on condition shall be a signalling tone conforming to the following parameters and shall attain a stable state within
43、 5 ms of application. Signal tone frequency The signalling tone shall be at a frequency of 2,280f 5 Hz. Signal tone power The tone-on condition shall have two power levels: a high level and a low level. A high level tone shall be sent for the duration of the signal or for a minimum of 300 ms (whiche
44、ver is shorter) and for a maximum of 550 ms after which it must be reduced to low level. (a) A high level tone-on condition shall be a signalling tone transmitted at a level of - 10 dBmO* 1 dB. (b) A low level tone-on condition shall be a signalling tone transmitted at a level of -20 dBmO* 1 dB. Lon
45、g-term mean power during signalling (a) In the frequency band 300-3,400 Hz, the long-term mean power applied to the transmit path, excluding the signalling tones, shall be at least 35 dB below the signalling tone power. (b) At frequencies in the range 3.4 to 50 kHz, the short-term mean power level o
46、f any spectral component shall not lie above the line shown on Figure 2 (T/CS 49-01). Note: Short-term here refers to a period not greater than 1 ms. (c) In any 3 kHz band contained above 3.4 kHz, the long-term mean power shall not exceed the level which would be permitted in accordance with (b) abo
47、ve for a spectral component at the mid-frequency of that band. Note: The requirements for the long-term mean power exclude any near end noise prior to splitting, according to CCITT Recommendation 4.25 4, see 4.1.3., but include noise attributable to the action of splitting. Tone-off condition A tone
48、-off condition requires the absence of signal tone and shall conform to the following: Edition of May 15, 1986 CEPT T/CS*49-OL*E 232b414 0004872 T dBm O - 20 - 33 -LO - 60 - 80 - 100 4.1.3. 4.1.3.1. 4.1.3.2. 4.1.4. 4.2. TICC 49-01 E Page 5 Figure 2 (T/CS 49-01). - the stable state shall be attained
49、within 5 ms of the commencement of the tone-off condition, and - the total power of any signalling tone that may be present in the tone-off condition (Le. the signal Sending-end splitting arrangements When a signal is to be sent on the line, the transmission path shall be split in accordance with CCITT Recommendation 4.25 4, from any source of near end speech or noise. Transmission path splitting shall occur within a period from 20 ms before to 15 ms after application of a tone-on condition. The transmission path restoration requirements may diff
