Low-Complexity
DTMF Digit Detection
by D2 Technologies, Inc.

Software Overview

D2's Low-Complexity DTMF Digit Detection algorithm module detects the presence of all 16 DTMF 
digits that are produced by different telephones on the market under a broad range of network 
conditions and under international telecommunications specifications. It meets EIA 464 and Bellcore 
requirements for tone detection and requires minimum hardware resource. D2's Low-Complexity DTMF 
detector is intended for "dialing" applications for customer premise equipment or telco equipment.
Designed to the VP Open interface, the Low-Complexity DTMF Digit 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, Low-Complexity 
DTMF Digit Detection consists of robust software that is rigorously tested.

Features and Benefits

•	Detects the presence of all 16 DTMF digits or 12 DTMF digits produced by different telephones
•	Detects leading and trailing edge
•	Meets or exceeds all Bellcore and EIA 464 tone detection requirements
•	Accepts telephone-band codec or linear data
•	Talk-off performance: exceeds Bellcore test tape talk-off requirements

Processor and System Specifications

•	Devices supported: TMS320C2xx, TMS320C3x, TMS320C5x
•	Algorithm category: Telecommunications
•	Processor resource required:
TMS320C2xx (Est.)
TMS320C3x (Est.)
TMS320C5x
Program memory
1.1 kwords
0.7 kwords
971 words
Data memory/port
40 words
35 words
40 words
Processor loading
worst case
1.3 MIPS
0.85 MIPS
1.2 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 Low Complexity DTMF Digit Detection algorithm module is validated through the following suite 
of tests:
•	D2's tone-detection test for tone duration, tone-frequency shift and twist, signal to noise, and 
tone levels (superset of Mitel and Bellcore tone tests)
•	Talk-off test with Mitel and Bellcore voice tapes
•	D2's set of talk-down tests (superset of Bellcore and Mitel tests) validate performance in the 
presence of echo, dial tone, white noise, and impulse noise
•	Detection of digits from a suite of telephone sets
•	VP Open interface validation – the Low-Complexity DTMF Digit 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 also available for the TI EVM50 
DSP board. Implementation for the TMS320C2xx and the TMS320C3x will be available 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