FAX/CNG Tone Detection
by D2 Technologies, Inc.

Software Overview

D2's FAX/CNG Tone Detection algorithm module detects the presence of a calling tone (CNG), the 
standard connection protocol for automatic connection of a FAX modem, and automatically routes the 
FAX to the answering party's FAX modem.
Designed to the VP Open interface, the FAX/CNG Tone Detection module easily integrates with other 
VP Open modules, runs in real-time concurrently with other VP Open modules, and handles any number 
of voice ports assigned to the DSP. Like all of D2's algorithm modules, FAX/CNG Tone Detection 
consists of robust software that is rigorously tested.

Features and Benefits

•	Detects the presence of the FAX calling tone (CNG)
•	Accepts linear or codec data

Processor and System Specifications

•	Devices supported: TMS320C2xx, TMS320C5x
•	Processor resource required:
•	Algorithm category: Telecommunications
TMS320C2xx (Est.)
TMS320C5x
Program memory
1 kwords
0.9 kwords
Data memory/voice port
140 words
138 words
Processor loading worst case
1.1 MIPS
1.0 MIPS

Usage Limitations or Performance Considerations

•	The host, voice data input and output, memory allocation, and module to module communication 
interfaces must conform to VP Open as described in the VP Open Software Interface Specification.

Algorithm Verification

D2's FAX/CNG Tone Detection algorithm module is validated through the following suite of tests:
•	D2 tone detection test with a prerecorded tape containing at least ten samples of each the CNG 
tone from at least five different FAX machines
•	D2 tone detection test consisting of CNG tone with various frequency shifts and power levels
•	D2 tone detection talk-down test
•	VP Open interface validation – the FAX/CNG Tone Detection module is integrated with other VP Open 
modules and tested concurrently in real-time on the D2 VDS50 system for multiple voice ports

Availability

Currently available for the TMS320C5x. A demonstration package is currently available for the TI 
EVM50 DSP board. The TMS320C2xx implementation will be available in 2Q 1996.

Company Background and Contact Information

D2 Technologies, Inc. was founded by David Y. Wong and David M. Lindsay to help companies innovate 
telecommunications and information products with voice processing technology, which include 
telephony and voice algorithms, real-time system software, and development services.

Contact:		D2 Technologies, Inc.
		Attn:  Product Sales
		104 West Anapamu Street
		Suite J
		Santa Barbara,  CA 93101
		(805) 564-3424
		Fax:  (805) 966-2144
		e-mail:  sales@d2tech.com