1、 CEPT NET*24 92 D 232b414 0011393 513 D NET 24 First edition: 1992 EUROPEAN TELECOMMUNICATION STANDARD Attachments to the Public Switched Telephone Network (PSTN) Category II attachment requirements for 1200 bits per second half duplex and 1200175 bits per second asymmetrical duplex modems standardi
2、zed for use on the PSTN Published by: CEP“ Liaison Office Seilerstrasse 22 CH-3008 Bern Telephone: Facsimile: Telex: 91 1089 CEPT CH + 41 3 1 62 20 8 1 + 41 31 62 20 78 CEPT NET*(, an 12 NET 24 CEPT NET*24 92 232b4L4 OOLL4LL 3b9 = indication shall be given from the DTE connected to the modem under t
3、est that it wishes to transmit data. During the time until the modem under test indicates to the DTE that it is ready to accept data from the DTE (equivalent: turning ON Cct 106), alternating binary 1 and binary O shall be output at the received data lead of the modem used for reference (equi- valen
4、t: Cct 104). A.6 Test for subclause 5.11.1 (Distortion) The following test pattern is specified for the tests described in subclauses A.6.1, A.6.2 and A.6.3: A cyclic string of discrete test characters (DTCs) consisting of DTC No. 2 + DTC No. 3 + DTC No. 2 + DTC No. 1 + DTC No. 2 + . . . as specifie
5、d in ETS 300 114 2, Annex B, subclause B.5.1.3 for the 10-bit character length. The test period for the tests described in subclauses A.6.1, A.6.2 and A.6.3 shall be one minute. A.6.1 Test for subclause 5.11.1 (a) The modem under test is connected to the modem used for reference via Test Line 3 (see
6、 NET 20 2, Annex C.5). The modem used for reference is caused to transmit the test pattern to the modem under test at a rate equal to the maximum bit rate for the channel under test, Le. 1200 bids or 75 bids. The degree of synchronous start-stop distortion of the re- ceived data output (equivalent:
7、Cct 104 for the data channel, or Cct 119 for the backward channel) of the modem under test shall not be greater than 15%. A.6.2 Testfor subclause 5.11.1 (b) The modem under test is connected to the modem used for reference via Test Line 1 without frequency offset (see NET 20 2, Annexes B.6.4 and C.3
8、) and transient impairments. The modem used for reference is caused to transmit the test pattern to the modem under test at a rate equal to the maximum bit rate for the channel under test, i.e. 1200 bit/s or 75 bit/s. The degree of synchronous start-stop distortion of the received data output (equiv
9、alent: Cct 104 for the data channel, or Cct 119 for the backward channel) of the modem under test shall not be greater than 35%. A.6.3 Test for subclause 5.11.1 (e) This test shall be performed twice: once with a frequency offset of +4 Hz and then with a frequency offset The modem under test is conn
10、ected to the modem used for reference via Test Line 1 without transient impairments (see NET 20 2, Annexes B.6.4 and C.3). The modem used for reference is caused to transmit the test pattern to the modem under test at a rate equal to the maximum bit rate for the channel under test, i.e. 1200 bids or
11、 75 bids. The degree of syn- chronous start-stop distortion of the received data output (equivalent: Cct 104 for the data channel, or Cct 119 for the back- ward channel) of the modem under test shall not be greater than 35%. Of -4 Hz. CEPT NET*24 92 m 2326414 OOLL4L2 2T5 m ANNEX B (INFORMATIVE) PROF
12、ORAMA DECLARATION OF MODES OF OPERATIONKJSE Declaration of modes of operatioduse for 1200 bids half duplex and 1200/75 bids asymmetrical duplex modems The modem submitted for approval is capable of operating in the modes indicated in the tables below. based on CCITT Recommendation V.23 4 TABLE B 1 P
13、roforma for declaring modes of use 14 NET 24 I 1200 bit/s half duplex I I a) Asynchronous I I I d) Synchronous I I I Asymmetrical duplex I 1 b) 1200/75 bit/s asymmetrical duplex I I I c) 75/1200 bids asymmetrical duplex I I TABLE B2 Proforma for declaring modes of operatioduse Auto-calling or auto-a
14、nswering a) Auto-calling b) Auto-answering TABLE B3 Proforma for declaring modes of operatioduse 1200 bids channel ready for sending indicator a) DTE control b) Control derived from the 1200 bit/s channel Ieabove methods TABLE B4 Proforma for declaring modes of operatioduse I 75 bit/s channel ready
15、for sending indicator I I a) controi I I I b) Control derived from the 75 bi/s channel I I CEPT NET*24 92 2326434 0011433 131 TABLE B5 Proforma for declaring modes of operatioduse Ready for sending response times a) 750 ms to 1400 ms for initial attempt I b) 20 ms to 40 ms I c) 200 ms to 275 ms I I TABLE B6 Proforma for declaring modes of operatioduse I Channel allocation for asymmetrical duplex modems a) Transmit on backward channel when forward b) Separate control of the forward and backward channel is off channels by the DTE NET 24 15
