0x275C Signal
(Interworking Only)

Used in:
0x0033 NPDI Universal ICB

Byte | Description
0, 1 | Tag 0x275C
2, 3 | Length Variable
4, 5 | Value[0-1] Signal Value 0x0000 Dial tone on 0x0001 Ring back tone on 0x0002 Intercept tone on 0x0003 Network congestion tone on 0x0004 Busy tone on 0x0005 Confirm tone on 0x0006 Answer tone on 0x0007 Call waiting tone on 0x0008 Off hook warning tone 0x0009 Preemption tone on 0x000A Tone off 0x0010 to 0x010F Alerting on pattern 0x00 to 0xFF (Cadence ringing type) All other values are reserved.

Network Protocol Data Intelligence. Also called “Interworking,” it is a software product that operates within Excel’s Call Control (Layer 4) and Services (Layer 5) call processing layers. NPDI is meant to enhance Excel’s call processing product offering by allowing call processing layers (specifically Layers 4 and 5) to perform advanced analysis, generation, and conversion of Network Signaling (NS) Layer 3 information.
See Information Control Block.
Pattern of tones and silence, such as a busy signal.