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20、he Interface Between DCEs and Voiceband Analog Channels Prepared by TR-30.3 Subcommittee on Data Communication Network Interfaces TSB 18-B This Engineering Bulletin is being issued in advance of the Standard for the “INTERFACE BETWEEN DATA CIRCUIT TERMINATING EQUIPMENT (DCE) AND VOICEBAND ANALOG LEA
21、SED LINES” in order to provide manufacturers of DCEs with timely information on this interface. This information reflects agreements reached between EIA Technical Subcommittee TR-30.3 and the representatives of Exchange Telephone carriers. Equipment conforming to this interface is already available
22、from many facility providers. This information will be incorporated in the Standard for the “INTERFACE BETWEEN DATA CIRCUIT TERMINATING EQUIPMENT (DCE) AND VOICEBAND ANALOG LEASED LINES” when it is issued. TSB 18-B Page 1 THE MECHANICAL/FUNCTIONAL CHARACTERISTICS OF THE INTERFACE BETWEEN DCEs AND VO
23、ICEBAND ANALOG CHANNELS 1.1 The interface between the DCE and the analog leased line is located at a pluggable connector. An 8-position keyed modular jack (female) is specified for the network side of this interface. The plug (male) associated with the DCE can either be keyed or unkeyed. To alleviat
24、e cross-talk, it is recommended that twisting pairs be used for interface cords exceeding 15 feet in length. 1.2 The interchange circuits, with their associated pin-pair relationships, should be assigned in accordance with Table 1 below (see Figure 1). 1.3 DCE MANUFACTURERS SHOULD BE CAUTIONED THAT
25、THIS CONNECTOR IS USED IN A VARIETY OF APPLICATIONS AND THEREFORE UNSPECIFIED POTENTIALS COULD BE FOUND ON ANY OF THESE PINS. SPECIFICALLY, PINS 1 & 2 AND 7 & 8 HAVE BEEN ASSIGNED FOR OPTIONAL POWERING ARRANGEMENTS IN ISDN. PAIR/PIN INTERCHANGE CIRCUIT FROM DCE TO DCE 1/1* Transmit Signal (R1) X 1/2
26、* Transmit Signal (T1) X 2/3* TEK5 Loopback Indicator X 3/4 Reserved 2/6* TEK6 Loopback Indicator X 4/7 Receive Signal (T) X 4/8 Receive Signal (R) X Table 1: Interchange Circuit Assignments * This pair is used for 2-wire access. * When provided, an open circuit between TEK5 and TEK6 indicates that
27、the line is not available for transmission. This may be caused either by a loopback of the leased line towards the central office or an out of service condition. TSB 18-B Page 2 THE TELECOMMUNICATIONS INDUSTRY ASSOCIATION TIA represents the global information and communications technology (ICT) indu
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