Tone Detect and Suppress

The Adaptive Digital Technologies (ADT) Signaling Tone Detector Software signaling tone
detector that uses Adaptive Digital’s proprietary algorithm. It is robust both in detection
performance and efficient in its use of CPU cycles.

In addition to carrying speech signals, the telephone network is required to carry various
in-band signaling tones. Telephony equipment must pass these tones with little distortion
so they can be detected by receiving equipment. While speech compression works well
with speech signals, many speech compression techniques are unable to pass signaling
tones without excessive distortion. For these type of signals, a tone passer, consisting of
a tone detector and tone regenerator, is used to ensure the reliable passage of the
signaling tones.

ADT’s Signaling Tone Detector Software supports the following types of signaling tones:

•  Dual Tone Multi-Frequency (DTMF)
• Multi Frequency R1 (MFR1)
• Multi Frequency R2 Forward (MFR2F)
• Multi Frequency R2 Reverse (MFR2R)
• Call Progress (CPRG)

DTMF signaling has long been a standard for transmitting dialed telephone numbers in
telecommunications systems. DTMF signaling is used in virtually every POTS (Plain Old
Telephone Service) telephone. In addition to its use in placing telephone calls, DTMF
signaling has become used increasingly to browse through voice-mail menus and other
touch-tone activated systems.

Call Progress signals are used to indicate the state of the call being made.

An optional DTMF suppressor is available to suppress DTMF tones in Voice-Over-Packet systems that employ tone passing via out-of-band signaling. This is useful when a low rate speech compression algorithm is unable to pass the DTMF tones without significant distortion.