ADTRAN 624, 612, 616, 606, 604 system manual DS0 Maps EDIT/VIEW MAP 1 RBS

Total Access 600 Series System Manual Section 4 User Interface Guide

DS0 MAPS > EDIT/VIEW MAP 1 > RBS

Voice applications require signaling information to identify the state of the channel. In some voice networks a dedicated signaling channel is available to accomplish this (for example, ISDN with a dedicated D channel). Traditional voice networks may employ Robbed Bit Signaling (RBS), also known as Channel Associated Signaling (CAS), where a dedicated signaling channel is unavailable. RBS permanently encodes signaling information by “robbing” a single bit from designated T1 frames and using them as signaling information carriers. The actual location of the signaling information within the T1 frame depends on the framing format of the T1 circuit. For SuperFrame (SF) framing, the T1 channel is comprised of 12, 193-bit frames (192 data bits plus a single framing bit). RBS “robs” the framing bits from the even numbered frames (2, 4, 6, etc) to provide signaling information for that channel. The signaling bits provided in these frames are known as the A and B signaling bits.Voice termination devices use the various combinations of the signaling bits to identify the current state of the voice circuit. Each signaling type (Loop Start, Ground Start, E&M, etc) uses varying combinations of A and B bits to identify the various states of the circuits such as ringing, on-hook, and off-hook. Extended Superframe (ESF) framing is similar to SF in operation. Each ESF T1 channel is comprised of 24, 193-bit frames (192 data bits plus a single framing bit) and allows bit “robbing” in frames 6, 12, 18, and 24. These signaling bits are known as the A, B, C, and D signaling bits, respectively. Again, voice termination devices use the various combinations of the signaling bits to identify the current state of the voice circuit.

The default value for this parameter is N/A. Once a port is assigned to a service (using the SERVICE field), this parameter changes to ON or OFF (depending on the selected service). ON preserves the signaling bits between the connections and is typically required for analog voice connections; therefore, for FXS interfaces, RBS defaults to ON. Additionally, when passing voice circuits with in-channel signaling through to the DSX-1 interface, signaling bits are preserved by setting RBS to ON. For clear channel service to the DSX-1 interface (for voice circuits with a dedicated signaling channel and all data) set RBS to OFF (which ignores the signaling bits). When SERVICE is set to T1 IAD, the RBS parameter remains at N/A because RBS is not applicable to data connections.

Map 2 menus are identical to Map 1. Please use the menu explanations above for Map 2.

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