scope:

This standard provides network-to-customer installation (CI) interface requirements for Direct Inward Dialing (DID) analog voicegrade switched access using loop reverse-battery signaling. DID is a feature of PBX and Centrex systems that permits direct access to a terminal served by a PBX or Centrex system from a carrier network without assistance from the PBX or Centrex attendant. The interface described in this standard uses loop reverse-battery signaling in connection with a one-way trunk that is outgoing from the network and incoming to the CI (see Figure 1.)

The loop reverse-battery signaling interface described in this standard employs a customer-installationprovided battery source. It is different from the interface described in T1.411-2001, Interface between carriers and customer installations - Analog voicegrade enhanced 911 switched access using networkprovided reverse-battery signaling, which describes an interface that uses reverse-battery signaling with a network-provided battery source.

Multiple carriers may be involved in providing the network transmission and signaling paths to the CI. Intermediate carrier-to-carrier interfaces are not covered in this standard. Also, this standard does not cover the voicegrade transmission performance of the network or the CI.

The network applies two types of signals to the Network Interface (NI):

- Normal telecommunication system voltages and currents; and

- Voltages and currents due to maintenance activities.

These are specified in this standard. Abnormal voltages and currents that are the result of the environment (e.g., induced voltages and currents, or lightning hits) 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 provide network-to-CI interface requirements for DID analog voicegrade switched access using loop reverse-battery signaling with a customer-installation-provided battery source. The requirements and recommendations are intended to assist carriers, manufacturers, and users of products to be used in or connected to the switched network to understand the characteristics of existing networks.