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CSA T512

Revision 91M, January 1, 1991

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Functional and Compatibility Requirements for Private Branch Exchange (PBX) Switching Equipment for Voiceband Applications

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Product Details:

  • Revision: Revision 91M, January 1, 1991
  • Published Date: January 1991
  • Status: Not Active, See comments below
  • Document Language: English
  • Published By: CSA Group (CSA)
  • Page Count: 252
  • ANSI Approved: No
  • DoD Adopted: No

Description / Abstract:

For the purposes of this standard, the PBX is considered to be a device that performs switching functions between station apparatus interfaces and between the station apparatus interfaces on one side and central office (CO) and special trunk interfaces on the other. Figure 1 shows two types of central office interfaces: communication interfaces that transmit and receive network supervisory and communication signais, and specialized interfaces, such as message registration and AIOD, which are used for allocating billing to outgoing calls. The interface on the station side is assumed to be com- I patible with the parameters specified in EIA-470A, Telephone Station instruments with Loop Signal- ing for Voiceband Applications (Ref A2), and EIA-478, Multi-Line Key Telephone Systems for Voiceband Applications (Ref A3). The requirements in this standard are intended to assure satisfactory user voicegrade services in a high percentage of installations both initially and over some period of time as the network grows and changes occur in telephone serving equipment.

Compliance with this standard is determined at the PBX interface boundaries (Fig 1) and is not to be construed as a constraint on the internal coding or switching techniques of the PBX. It is recognized that a PBX using some digital encoding, digital switching, analog modulation, and analog switching techniques will not meet some of the voiceband transmission requirements in Section 4.8 of this standard. However, maintenance of the overall quality of telecommunication performance requires that each connection through a PBX meets the category of transmission requhements specified in this standard with res* to the type of connection and to the PBX coding and switching technique employed. 

The standard recognizes that no one PBX design or installation need be equipped with ail types of interfaces contained herein. A PBX complies with this standard when it conforms to the requirements applicable to the interfaces with which it is equipped. For satisfactory service, a PBX should be capable, through the proper seledon of equipment options, of satisfying the requirements applicable to its serving area. The requirements for the individual types of PBX interfaces vary between telephone companies and in some cases between central office switching machines; therefore, in some cases multiple options are stated for satisfying a particular requirement.

The criteria for supeMsory and address signals sent toward the network assume that the PBX repeats or regenerates station apparatus dc signals received from the station apparatus. It is assumed that voiceband transmission from one port to a similar or different port of the PBX introduces some smd amount of degradation commensurate with satisfactory overall user and end-to-end performance.

The standard is intended to be in conformance with Part 68 of the FCC des (Ref A4) but it is not limited to the sccpe of those des. If Part 68 requirements are more stringent than those contained in this standard, the provisions of Part 68 apply. 

It is recognized that some PBX products may not be accommodated by this standard because of nonstandard line interfaces; Le., other than that described in 4.5. in such systems, the station apparatus must be considered as a whole with the PBX and its associated station wiring, and the overall system must be described in terms of an acoustic (user) to an electrical (network) standard.

The requirements in this document assume a ringer equivalence number (REN) of 5. if the PBX has a REN of less than 5, then the requirements designated by the parenthetical expression (REN) need to be appropriately scaled in accordance with Section 68.312 of the FCC Rules and I Regulation

In addition to the requirements in this standard, the safety requirements in UL 1459 (Ref A17) apply. The UL 1459 requirements may be more restrictive. Environmental considerations for I PBXS are found in Ref A5.