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Primary Rate Interface (PRI) and T1 Feature

Description

Signaling Mode

Signaling is the process of communicating channel-state information, such as dialing, from endpoint to endpoint. Two types of signaling can be used in T1 transmission: robbed-bit signaling (RBS) and common-channel signaling (CCS). Choosing a signaling mode is important only for T1 service; PRI always uses CCS (23 B-channels and 1 D-channel). The signaling types are as follows:

• Robbed-Bit Signaling. Robbed-bit signaling (RBS) replaces the least significant bit in every sixth frame of each DS0 channel with signaling information. RBS is also called in-band signaling because signaling information is embedded in the same channel that carries the user's voice or data in a call. Robbed Bit Signaling must be used if T1 Switched 56 service is to be used on the T1 connection.

• Common-Channel Signaling. Common-channel signaling (CCS) is an out-of-band signaling format that places the signaling bits for channels 1 through 23 into the 8-bit word of the twenty-fourth channel. This restricts DS1 from using the twenty-fourth channel for voice or data transmissions. D4 framing does not preclude the use of CCS, but CCS is not compatible with D4 channel banks because the D4 channel banks recognize only RBS. CCS is used when PRI service is desired on the DS1 facility.
  
  

If you have a 100D module with an apparatus code of 517M15, common-channel signaling is not an option for T1.

ESF framing should be used because of its improved maintenance, diagnostic, and testing capabilities. If the transmission between two systems is voice-only, RBS should be used for all 24 communications paths. For voice transmissions, both ZCS and B8ZS line coding can be used to satisfy the ones-density requirement: the preferred line-coding format is B8ZS, which is needed for 64-kbps digital data.

The framing and signaling formats depend on the network and interconnection devices (CSUs) used. For example, the 551 T1 L1 CSU supports only ZCS.

Through PRI, digital data using up to 64 kbps is possible only when using a DS1 facility; connections of up to 64 kbps for each channel are also possible on BRI connections. Also, ESF framing mode, CCS signaling, and B8ZS line coding are required. An ACCULINK 3150/3160/3164 or ESF-T1 CSU must be used for DS1 connections within a building.

Topics
	Description
	Called Party Nunber (CdPN) Calling Party Number (CPN) Lines / Trunks PRI T1 DS1 Facility Options Type of Service Framing Format Line Coding Channel Service Unit   Line Compensation Signaling Mode Tandem PRI Trunks Tandem PRI Trunk Programming PRI Programnming Options PRI Programnming Options - PRI Telephone Number PRI Programnming Options - Network Services Supported PRI Programnming Options - Copy Telephone Number to Send PRI Programnming Options - Telephone Number to Send PRI Programnming Options - Test Telephone Number   PRI Programnming Options - Timers and Counters PRI Programnming Options - Terminal Equipment Identifier (TEI) PRI Call Processing Incoming Calls Outgoing Calls Network Selection Table Call-by-Call Services Table Station Identification - Automatic Number Identification T1 Programming Options T1 Programming Options - T1 Tie Trunk Connections T1 Programming Options - T1 Routing by Dial Plan System-wide Programming Options - Clock Synchronization System-wide Programming Options - Clock Switching
	At a Glance
	Considerations & Constraints
	Incoming Calls Outgoing Calls
	System Programming
	Mode Differences
	Feature Interactions