DTMF
Digit Detection and Removal
by D2 Technologies, Inc.

Software Overview

D2's DTMF Digit Detection and Removal 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. This module includes rapid detection and 
removal algorithms that eliminate DTMF tones within 12 msec of tone onset. D2's robust DTMF 
detector is designed for dialing, voice mail, IVR, and voice-conferencing applications.
Designed to the VP Open interface, the DTMF Digit Detection and Removal 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, DTMF Digit 
Detection and Removal 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; 
eliminates DTMF signal within 12 msec of tone onset
•	Superior talk-off performance: no talk-off on Mitel test tape and under 20 talk-offs for Bellcore 
test tape
•	Detects leading and trailing edge and eliminates tone bounces; programmable twist, dynamic range, 
and tone duration: 24, 32, and 40 msec
•	Superior talk down performance with D2's network echo canceller
•	Meets or exceeds Bellcore and EIA 464 tone detection requirements

Processor and System Specifications

•	Devices supported: TMS320C2xx, TMS320C3x, TMS320C5x
•	Processor resources required:
•	Algorithm category: Telecommunications
TMS320C2xx (Est.)
TMS320C3x (Est.)
TMS320C5x
Program memory
2.4 kwords (DTMF detect), 0.3 kwords (DTMF remove)
2.7 kwords (DTMF detect), 0.4 kwords (DTMF remove)
2.4 kwords (DTMF detect), 0.3 kwords (DTMF remove)
Data memory/
voice port
218 words (DTMF detect and remove)
218 words (DTMF detect and remove)
218 words (DTMF detect and remove)
Processor loading
worst case
2 MIPS (DTMF detect), 0.4 MIPS (DTMF remove)
1.5 MIPS (DTMF detect), 0.2 MIPS (DTMF remove)
1.75 MIPS (DTMF detect), 0.25 MIPS (DTMF remove)

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 DTMF Digit Detection and Removal validation tests:
•	D2's tone detection tests (superset of Mitel and Bellcore) for tone duration, tone frequency 
shift and twist, signal to noise, and tone levels
•	D2's talk-off tests - include Mitel and Bellcore tests
•	D2's debounce test for long tones with echo
•	D2's talk-down test of 1600 DTMF digits for 144 different combinations of DTMF level, echo level, 
and canceller settings
•	D2's set of DTMF detection tests (superset of Mitel and Bellcore tests) for 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

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

Contact:	D2 Technologies, Inc.
		104 West Anapamu Street, Suite J
		Santa Barbara,  CA 93101

		(805) 564-3424
		Fax:  (805) 966-2144
		e-mail:  sales@d2tech.com