scope:

This standard provides the signaling and data transmission requirements associated with the following supplemental features that utilize network-originated on-hook data transmission on analog voicegrade switched access lines that use loop-start signaling:

- Calling Number Delivery (CND);

- Calling Name Delivery (CNAM);

- Visual Message-Waiting Indicator (VMWI).

The use of the CND, CNAM, or VMWI supplemental features with Integrated Services Digital Network (ISDN) access lines is beyond the scope of this standard.

This standard is intended to be used in conjunction with American National Standard for Telecommunications - Interface between carriers and customer installations - Analog voicegrade switched access lines using loop-start and ground-start signaling, ANSI T1.401-1993. The on-hook data transmission features described in this standard may not be available on access lines that utilize ground-start signaling.

The supplemental features provide information about the calling access line to the called access line or information about a message that is waiting to be retrieved. Customer installation equipment that receives the information associated with these services can normally display, print, or store the information, however, such capabilities are outside of the scope of this standard.

Requirements in this standard are specified at the interface between telecommunications carriers, and customer premises cabling and equipment. In this standard, the telecommunications carrier network is referred to as the network and customer premises cabling and equipment is referred to as the customer installation (CI). The interface between the network and the CI is referred to as the Network Interface (NI).

The signals that the network presents at the NI are basically of two types: normal telecommunications system voltages and currents, and voltages and currents due to maintenance activities. The normal signals are specified in this standard. Abnormal voltages and currents that are the result of the environment (e.g., induced voltages and currents or lightning) are not covered in this standard.

Tariffs, contracts, or regulatory acts in various jurisdictions may contain additional or more stringent requirements than those in this standard.

Purpose

The purpose of this standard is to assist manufacturers, and users of products to be connected to the network to understand the characteristics of carrier networks when supplemental features that provide network-originated on-hook data transmission are provided on analog voicegrade switched access lines that use loop-start signaling. The interface requirements may be useful in minimizing incompatibility problems although this standard is not intended to be an equipment specification.

Application

This standard assumes the existence of an analog voicegrade switched access line with a supplemental feature that provides network-originated on-hook data information. Availability of these features depends on the network equipment serving the NI. These supplemental features may not be available at all loop-start NIs. These supplemental features can only be provided if the network switching system serving the CI is a stored program control switching system (SPCS). For interswitch calls, the CND and CNAM features require common channel signaling between switching systems in order to receive the calling line directory number (DN) at the terminating SPCS. When the features in this standard are provided, other supplemental features may not be available (e.g., network-implemented coin-operated payphone feature).

The standard assumes that customer premises equipment (CPE) exists at the CI that can receive network- originated on-hook data transmission using the single data message format (SDMF) and the multiple data message format (MDMF). Such equipment is sometimes called Type 1, Type 2, or Type 3 CPE. Other CPE, which can receive on-hook data transmission only in the SDMF, does not fit into any of the previously mentioned CPE categories. It is possible for such equipment to support the CND and VMWI features but not the CNAM feature.

Because of the wide range of network switching systems, customer loop plant, network transport systems, and CIs in North America, conformance with this standard does not guarantee interface compatibility under all possible operating conditions. In addition, the interface described in this standard may not be universally available.

The supplemental features described in this standard may not be available if network transport facilities will not support on-hook data transmission in the SPCS-to-CI direction.

This standard is intended to be used in conjunction with American National Standard for Telecommunications - Interface between carriers and customer installations - Analog voicegrade switched access lines using loop-start and ground-start signaling, ANSI T1.401-1993. It is one of a series of interface standards prepared by the Network Interfaces Technical Subcommittee of Committee T1.

The provisions of this standard are intended to be consistent with applicable requirements concerning safety and environmental conditions.