1、CEPT T/CS*49-12*E = 232b4L4 0005LL2 2 I SEND SIGNALLING i/ PATH PABX TERMIN4TION 0 T/Cs49-12 Page E 1 Recommendation T/CS 49-12 (Vienna 1982, revised in Montpellier 1984) SYSTEM L2 SIGNALLING ON EXTRA LONG LINES BETWEEN A TELEPHONE INSTRUMENT OR EQUIVALENT AND A PUBLIC EXCHANGE OR PRIVATE AUTOMATIC
2、BRANCH EXCHANGE Recommendation proposed by Working Group T/WG 1 1 “Switching and Signalling” (CS) Revised text of the Recommendation adopted by the “Telecommunications” Commission: “The European Conference of Postal and Telecommunications Administrations, considering that there is an increasing need
3、 for connection of a telephone instrument or its equivalent to an exchange (public or private automatic branch exchange) where the normal loop limits are exceeded; that in certain cases telephone instruments or their equivalent in one country have to be connected to exchanges in another; that these
4、extra long connections should permit a fully automatic operation from telephone instruments or their equivalent to exchanges, recommends that members, when introducing international connections of telephone instruments or their equivalent in one country to public exchanges or private automatic branc
5、h exchanges (PABXs) in another, use the signalling System L2, which is comprised of the signals, signalling procedures, and equipment functions specified in the following.” 1. PRINCIPLES AND FIELDS OF APPLICATION SIGNAL OUTPUT Figure 1 (TICS 49-12). Edition of May 15, 1986 CEPT T/CS*49-12*E 2326414
6、0005113 4 TICC 49-12 E Page 2 1.4. 1.5. 1.6. 1.7. 1.8. 1.9. 1-10. 1.11. 2. 2.1. 2.2. 2.3. 2.3.1. The system is a single voice,frequency (I vf) line signalling system using a signalling frequency of: - 2,280 Hz in both directions on four-wire circuits; - 2,280 Hz in the direction ISU to ESU and 2,400
7、 Hz in the direction ESU to ISU on two-wire circuits. The use of voice frequency signals renders the system suitable for all voice transmission media, except those using speech interpolation. The line supervisory system may be used to convey digit signals at 10 pulses/second (pps), or as an adjunct
8、to multifrequency push-button (MFPB) signalling. Signals are sent as either application of signalling frequency tone-on or removal of signalling frequency cone-off in continuous or pulsed form. When in the idle condition, the signalling frequency applied to the line by the ISU is reduced in power le
9、vel to conform to the transmission loading requirements of CCITT Recommendation Q. 15 i. The signalling system allows through dialling of 10 pps or multifrequency push-button type (MFPB) to subsequent circuits, e.g. to another PABX or public exchange. The line supervisory signals are contained withi
10、n the ISU-ESU link and not allowed to spill over into the next link. When making an outgoing call, a through speech path shall be provided in the ESU-ISU direction of transmission during call Set-up. Signals may be passed in the direction ISU to ESU while speech or audible indications are being rece
11、ived in the direction ESU to ISU. These specifications define the signalling requirements of the system in terms of electrical conditions, and their persistance before they may be regarded as valid signals. SYSTEM L2 SIGNALS General The names and meanings of the signals specified for System L2 are i
12、n accordance with Recommendation T/CS 41-01 2. According to their use in signalling System L2, some special functions may apply. Therefore, a further description is given in Section 2.3. below. Line signals The signals transmitted over the line are shown in Table 1 (T/CS 49-12). They are divided int
13、o two categories: i) signals that are essential in a basic version: Mandatory (M); ii) signals which could be used to supply optional facilities when required: Optional (O). Signals I ISU to ESU I ESU to ISU - I I Idle Calling Seizing Address information Answer Recall Metering Clear M M M M O M - Ta
14、ble 1 (T/CS 49-12). System L2 signals. Functions of the signals and states Signals sent from ISU to ESU 2.3.1.1. Mandatory signals Idle signal In the idle state the ISU applies a tone-on condition to the line to indicate it is free to accept calls (see Tables 2 (T/CS 49-12) and 3 (T/CS 49-12). Editi
15、on of May 15, 1986 CEPT T/CS*49-L2*E 232b4L4 0005114 b TICS 49-12 E Page 3 Seizing signal When the telephone instrument changes from on-hook to off-hook, the ISU applies a seizing signal to the signalling path. On recognition of the seizing signal, the ESU informs the exchange that the telephone ins
16、trument is Address information Address information (routing digits and telephone number) is sent either in the form of signalling tone pulses (decadic pulses) or as MFPB signals. Answer signal When the called telephone instrument changes from the on-hook to the off-hook condition, the ISU applies an
17、 answer signal to the signalling path. On recognition of the answer signal, the ESU informs the exchange that the telephone instrument is in the off-hook condition and that ringing must be stopped. Clear signal When the telephone instrument is put in the on-hook condition, the ISU applies a clear si
18、gnal to the signalling path. On recognition of the clear signal, the ESU informs the exchange that the telephone instrument has been put on-hook. Provision of the following optional signals and procedures depends on network requirements, and is subject to mutual agreement by the parties involved. Re
19、call signals On receipt of a recall signal from the telephone, the ISU applies a recall signal in the form of a tone-on pulse to the signalling path. The length of tone-on pulse applied by the ISU depends upon the type of recall employed by the associated telephone, e.g. timed break or earthed loop.
20、 Signals sent from ESU to ISU Calling signal The calling signal is sent by the ESU to indicate that ringing current is being sent by the exchange. The calling signal is sent by the ESU as a series of tone-on pulses, in step with the periods of ringing current that are sent by the exchange. On recogn
21、ition of each tone-on pulse of the calling signal, the ISU applies ringing current to the telephone instrument. off-hook. 2.3.1.2. Optional signals and procedures 2.3.2. 2.3.2.1. Mandatory signals 2.3.2.2. Optional signals Provision of the following optional signals and procedures depends on network
22、 requirements and is subject to mutual agreement by the parties involved. Answer signal The answer signal is sent by the ESU to indicate that the called party has answered. Metering signals If the public exchange can send metering pulses for call charging, these pulses may be: i) sent during speech
23、in the voice band with appropriate safeguards to prevent the pulses from being heard; ii) sent during speech by application of channel splitting equipment (see CCITT Recommendation H.34 3), using one of the telegraph channels; iii) stored or sent, possibly on demand, at the end of the call. However,
24、 the handling of metering signals is outside the scope of this Recommendation. Edition of May 15, 1986 CEPT T/CS*49-L2*E m 2326434 000.5315 8 m I Speed (PPS) 7 LINE SIGNALLING SENDING AND DETECTING REQUIREMENTS 9 11 12 Signalling code The signalling code shall be as shown in Tables 2 (T/CS 49-12) an
25、d 2 (T/CS 49-12). Signal sending and detection requirements are given in paragraphs 3.2. and 3.3. I Signai Idle Se i z i n g Address information Answer (optional) Recall (optional) Clear Conditions from ISU Continuous tone-on Continuous tone-off Decadic pulsing or MFPB Recall tone-on pulse Continuou
26、s tone-on Conditions from ESI Continuous tone-off Tone-on pulse - Table 2 (T/CS 49- 12). Calls originated by the telephone instrument. Signal Idle Calling Answer Recall (optional) Clear Conditions from ESU Continuous tone-off Calling tone-pulse - Conditions from ISU Continuous tone-on Continuous ton
27、e-off Recall tone-on pulse Continuous tone-on - 3.2. 3.2.1. 3.2.2. 3.2.3. 3.2.3.1. Break pulse I Mi; y; Min Max Min Max Min Max Duration (ms) I 45 81 I 45 61 I 45 52 Legend: pps = pulses per second. Table 4 (T/CS 49-12). Where decadic pulses are generated within the ISU, the speed and break pulse du
28、ration applied to the transmit signalling path shall be either: (a) iOk0.5 pps with break pulse limits of 60-68%; (b) IO* 1 pps with break pulse limits of 59-66%. Edition of May 15, 1986 CEPT T/CS*49-L2*E 2326434 000533b T a 3.2.3.2 3.2.4. 3.2.5. 3.2.6. 3.3. 3.3.1. 3.3.2. 3.3.3. 3.3.3.1 TICS 49-12 E
29、 Page 5 Inter-digit pause Adjacent digits are separated by an inter-digit pause (IDP). The inter-digit pause is a function of the source of the digits, i.e. under control of a dial, or repeated, or generated by a signalling unit. This period, which will differ depending upon the Administration conce
30、rned and the type of equipment, is not specified in this Recommendation and must be mutually agreed upon by the parties involved. During the inter-digit pause, the backward speech path should be re-established. MFPB signals See CEPT Recommendation T/CS 46-02 4. Tone-on pulse signal A tone-on pulse s
31、ignal shall be the application of a tone-on condition to the send signalling path for a period of 45 to 135 ms. Recall tone-on pulse signal The length of recall tone-on pulse signal will depend on the type of recall applied by the associated telephone. A recall tone-on pulse signal, as a consequence
32、 of a timed break recall signal from the telephone (see paragraph 2.3.1.2.), shall be the application of tone-on condition to the transmit signalling path for a period of 50-130 ms, see Recommendation T/CS 20-09 5. A recall tone-on pulse signal, as a consequence of an earthed loop recall from the te
33、lephone (see para- graph 2.1.2.1.), shall be the application of tone-on condition to the transmit signalling path for a period of 210-240 ms. Culling tone-on pulse signals Calling tone-on pulse signals shall be the application of tone-on condition to the send signalling path, in step with the ringin
34、g period of the ringing cadence. Detection of signals Electrical conditions conforming to the requirements of paragraphs 4.2. and 4.4. applied to the line termination shall be regarded as a potential signal and referred to in the following as tone-on condition or tone-off condition. Signals are rece
35、ived as either a tone-on or a tone-off condition on the receive signalling path in a continuous or pulsed form. To discriminate between signals having similar characteristics and between signals and spurious electrical conditions, it is necessary to state the minimum persistence time for a potential
36、 signal. A signal is not valid 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 3.3.1. to 3.3.6. detail the minimum persistence of a defined electrical condition
37、 before it becomes a signal, i.e. a valid electrical condition persisting for less than the stated period shall not be recognised as a signal. The period in which a validated electrical condition must be recognised as a signal is a function of the ISU logic and is not given in these specifications.
38、However, recognition should occur as soon as possible following expiration of the stated persistence check period. Continuous tone-on signal A tone-on condition applied to the receive signalling path line termination is a continuous tone-on signal for signalling, when it has persisted for 250 ms. Co
39、ntinuous tone-of signal A tone-of condition applied to the receive signalling path line termination is a continuous tone-ofSsigna1 for signalling, when it has persisted for 40 ms. A ddress in for mat ion Address information is conveyed in decadic or MFPB form. Decadic pulsing Pulses of tone-on condi
40、tion applied to the receive signalling path line termination of the ESU, consistent with the speed and duration limits of Table 5 (T/CS 49-12), are break periods of decadic pulses. Each break pulse is separated from the next by a make pulse, i.e. tone-off condition. Within a digit, adjacent pulses m
41、ay differ in speed and duration and any combination of break pulses within the limits of Table 5 (T/CS 49-12) shall be accepted as decadic pulses. a , Edition of May 15, 1986 4 CEPT T/CS*49-L2*E = 232b414 0005LL7 1i = Speed (PPS) 7 9 11 Break pulse Min Max Min Max Min Max Duration (ms) 35 122 35 91
42、35 71 1 T/CS49-12 E Page 6 12 Min Max 35 62 4. LINE SIGNALLING TRANSMISSION REQUIREMENTS (FOUR-WIRE WORKING) 4.1. Signai sender, ESU Signals are sent by the ESU as either tone-on or tone-off condition applied to the send signalling path. Tone-on condition shall be a signalling tone conforming to the
43、 following parameters and shall reach a stable state within 5 ms of application. The signalling tone shall be at a frequency of 2,280 f 5 Hz. 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 minimu
44、m of 300 ms (whichever is shorter), and for a maximum of 550 ms after which it must be reduced to low level. (a) A high level lone-on condition shall be a signalling tone transmitted at a level of -10 dBmOf 1 dB. (b) A low level tone-on condition shall be a signalling tone transmitted at a level of
45、-20 dBmO+ 1 dB. Long-term mean power during signalling (a) In the frequency band 300-3,400 Hz, the long-term mean power applied to the send 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 mea
46、n power level of any spectral component shall not lie above the line shown on Figure 2 (T/CS 49-12). Note: Short-term here refers to a period not greater than 1 ms. 4.1.1. Tone-on condition 4.1.1.1. Signal tone frequency 4.1.1.2. Signal tone power 4.1.1.3. Edition of May I O 5. 1986 CEPT T/CS*49-12*
47、E 2326414 0005118 3 . dBm O - 20 - 33 -40 - 60 - 80 - 100 4.1.2. 4.1.2.1. 4.1.2.2. 4.1.3. 4.1.4. 4.2. 4.2.1. 4.2.1.1. I 4.2.1.2. I 3.1 TICS 49-12 E Page 7 2 Figure 2 (T/CS 49-12). (c) In any 3 kHz band contained above 3.4 kHz, the long-term mean power shall not exceed the level which would be permit
48、ted in accordance with (b) above for a spectral component at the mid-frequency of that band. Note: The requirements for the long-term mean exclude any near end noise prior to transmit path isolation, see paragraph 4.1.3., but include noise attributable to the action of transmission path isolation. T
49、one-off condition A tone-off condition is the removal of signal tone and shall conform to the following. Stable state A stable state shall be attained within 5 ms of commencement of the tone-off condition. Signal frequency leak The total power of any signalling tone that may be present in the tone-off condition shall exceed -70 dBmO. Transmission path isolation When a signal is to be sent, the transmission path shall be isolated from any source of near end speech or noise. Transmission path isolation shall occur within a period from 20 ms before to 15 ms after applicati
