scope:

This standard provides the requirements associated with three different types of call waiting supplemental features that may be used on analog voicegrade switched access lines with loop-start signaling. The three features are called:

- Call Waiting (CW);

- Distinctive Call Waiting (DCW);

- Calling Identity Delivery on Call Waiting (CIDCW).

This standard is intended to be used in conjunction with the following standards:

- American National Standard for Telecommunications - Interface between carriers and customer installations - Analog voicegrade switched access lines using loop-start and ground-start signaling, T1.401-1993;

- American National Standard for Telecommunications - Network to Customer Installation Interfaces - Analog Voicegrade Switched Access Lines with the Calling Number Delivery, Calling Name Delivery, or Visual Message Waiting Indicator Feature, T1.401.03-1998.

The CW feature provides a customer installation (CI), that is off-hook during the communications state of an originating or terminating call, with a CW tone to alert the CI that an incoming call is waiting to be answered. The CI can place the current call on hold and answer the incoming call by generating a flash signal.

The DCW feature is provided on switched access lines that also have a supplemental feature that provides distinctive ringing patterns for some incoming calls. The DCW customer may specify a list of telephone numbers that will initiate the DCW feature when calls are received from those switched access lines. The DCW feature provides a CI, that is off-hook during the communications state of an originating or terminating call, with a DCW tone pattern, if the call that is waiting to be answered is from a switched access line that matches a telephone number on the DCW list, to alert the CI that an incoming call is waiting to be answered. The CI can place the current call on hold and answer the incoming call by generating a flash signal.

The CIDCW feature is provided on switched access lines that have the CW or DCW feature and a Calling Identity Delivery feature such as the Calling Number Delivery feature or Calling Name Delivery feature, or both the Calling Number Delivery and Calling Name Delivery features. The CIDCW feature provides a CI, that is off-hook during the communications state of an originating or terminating call, with a CW tone followed by a CI Alerting Signal and a network-originated data message or a DCW tone pattern followed by a CI Alerting Signal and a network-originated data message when an incoming call is waiting to be an- (R2005) T1.401.04-2000 2 swered. The data message delivers the caller's identity, that is, the caller's number, the caller's name, or the caller's name and number. The CI can place the current call on hold and answer the incoming call by generating a flash signal.

The CI that receives CIDCW information can normally display, print, or store the information, however, such capabilities are outside of the scope of this standard.

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

The features described in this standard may not be available on switched access lines that utilize groundstart signaling.

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. Voltages and currents due to maintenance activities and 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 the CW, DCW, or CIDCW supplemental feature is provided on an analog voicegrade switched access line that uses 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 is applicable to network-to-customer installation interfaces for analog voicegrade switched access lines with loop-start signaling and either the CW, DCW, or CIDCW feature. This standard may also be applicable to certain network-to-network interfaces. In this situation, by mutual agreement, one of the networks shall meet the network specifications of this standard and the other network shall meet the customer installation specifications of this standard.

Availability of the supplemental features described in this standard depends upon the network equipment serving the NI. These supplemental features may not be available on all loop-start switched access lines. For example, the CIDCW feature can only be provided if the network switching system serving the CI is a stored program control switching system (SPCS) that has CIDCW capability. Also, for interswitch calls, the CIDCW feature requires common channel signaling between network switching systems in order for the terminating SPCS to receive the number or name associated with the calling switched access line.

When one of the features described in this standard is provided on a switched access line, other supplemental features may not be available on the same switched access line. (See 4.1.3 for examples.) (R2005) T1.401.04-2000 3 For the CW and DCW features, this standard assumes that customer premises equipment (CPE) exists at the CI that can generate a valid flash signal.

For the CIDCW feature, this standard assumes that there is Type 2 or Type 3 customer premises equipment (CPE) at the CI that can:

- Detect a CI Alerting Signal (CAS);

- at the appropriate time with an Acknowledgment (ACK) signal;

- Receive network-originated off-hook data messages that use the multiple data message format (MDMF).

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