PowerCall for OTFOTF, Commetrex’ S.100 middleware, is licensed without media-processing resources. PowerCall for OTF adds S.100-conforming signal generation-detection capability and in-band call-progress analysis to an OTF system. The PowerCall OTF SDK provides the necessary development environment; runtime licenses add a specific number of runtime resources to an OTF system.

The PowerCall for OTF SDK provides an ECTF S.100 Signal Generator-Detector API. It is used with the System Call Router (place call/accept call) and other OTF Services APIs by the telecommunications system developer to produce digital-media telephony applications.

Telephony applications that use the public switched telephone network for outbound calling require the ability to accurately and rapidly interpret the call-progress tones, such as ringback and busy, that are delivered by the network to the calling entity. This Call Progress Analysis (CPA) is complicated by the lack of the worldwide use of standard tone frequencies and patterns. The design of PowerCall signal-processing software, therefore, must address the tradeoff between speed of analysis and generality. Commetrex’ CPA is designed to minimize support requirements by providing an analysis resource that does not require tuning for over 99% of applications, even for global deployments, while providing fast, accurate responses.

Commetrex’ Signal Generator/Detector (SGD) furnishes all necessary functionality at the physical-layer level to support in-band telephony-signaling functions. Specifically, the SGD implements signal-processing to generate and detect DTMF and Multi-frequency (MF) (R1/R2) digits as well as any generic in-band tone comprised of up to two frequencies. The SGD is compliant with the ITU Q.24 recommendation.

Features

Benefits

Overview

OTF is an ECTF S.100 R2-conforming telephony middleware product that supports both third-party and Commetrex-provided media and switching resources. These vendor- specific resources are isolated from the OTF system by Resource Service Managers (RSMs). The resource-specific RSM determines the number of concurrent media- technology resources that have been licensed. The RSM then launches the appropriate Resource Controllers. Licensing the PowerCall SDK adds the CPA and Signal Generator- Detector Resource Controller to an OTF system. The RSM will then vend the licensed runtime resources to the OTF Group Manager, which can then allocate them to client applications.

The signal generation and detection functions of PowerCall may be directly accessed by an application program using the supplied S.100- conforming API. The tone generation and CPA functions are also invoked on behalf of applications that place calls through OTF’s System Call Router (SCR). The SCR API presents a network-access-independent interface to the application. Should the target of a CTscr_MakeCall() command be a network interface that requires DTMF dialing and in- band CPA, these functions will be invoked by the appropriate resource service manager on behalf of the SCR.

DTMF/MF and Precise Tone Generation

The Signal Generator is controlled by one function, CTsg_SendSignals(). The tables that follow show the user-defined parameters for DTMF, MF, and a generic tone generation.

DTMF and MF Parameters

Parm Name Type Default Units Description
Level 1 INT -6 dBm The level of the low frequency component of the DTMF pair. Valid range – 43 to –3.
Level 2 INT -4 dBm The level of the high frequency component of the DTMF pair. Valid range – 43 to –3.
LongPause INT 5000 Msec The delay associated with the ‘.’ (period) character. Valid range 0-65535.
Off Time INT 55 Msec The duration of the silence time between each DTMF digit. Valid range is 0–65535.
On Time INT 45 Msec The duration of each DTMF digit. Valid range is 0–65535.
ShortPause INT 2000 Msec The delay associated with the ‘,’ (comma) character. Valid range 0-65535.

Generic Tone Parameters

Parameter Name Type Default Units Description
Level 1 INT -20 dBm The level of the first (or only) frequency component. Valid range – 43 to –3.
Level 2 INT -4 dBm The level of the second frequency component (if any). Valid range – 43 to –3.
OffTime INT 0 Msec The duration of silence between tones on time. Specify 0 for no off-time. Valid range 0-65535.
OnTime INT 200 Msec The duration of the tone. Valid range is 1–65535.
FREQ1_Parm_1 INT N/A N/A Parameter 1 of the first (or only) frequency of the generated tone. Must be S.10 fixed point format. This parameter is computed from the desired frequency.
FREQ1_Parm_2 INT N/A N/A Parameter 2 of the first (or only) frequency of the generated tone. Must be S.10 fixed point format. This parameter is computed from the desired frequency.
FREQ2_Parm_1 INT N/A N/A Parameter 1 of the second frequency of the generated tone. Must be S.10 fixed point format. This parameter is computed from the desired frequency.
FREQ2_Parm_2 INT N/A N/A Parameter 2 of the second frequency of the generated tone. Must be S.10 fixed point format. This parameter is computed from the desired frequency.
Iterations INT 1 Integer The number of times to repeat the alternating tone and silence period. A count of –1 means repeat forever*. Otherwise the valid range is 1 to 32767.

* Therefore, if the Iterations parameter is set –1 and the Off-time parameter is set to 0, a continuous tone is produced.

DTMF and Precise Tone Detection
Tone detection is controlled by two commands: CTsd_FlushBuffer() and CTsd_RetrieveSignals().

DTMF Tone Parameters

Parm Name Type Default Units Description
OffQualLevel INT -43 dBm The minimum signal level required to maintain recognition of a DTMF signal once recognition has started. The valid range is –43 to –15.
OffQualTime INT 40 ms The minimum duration of absence of a recognized DTMF signal before end-of-digit event will be emitted. The valid range is 5 to 32767.
OnQualLevel INT -39 dBm The minimum signal level recognized as a DTMF signal. The valid range is –43 to –15.
OnQualTime INT 40 ms The minimum duration of a recognized DTMF signal before a digit event will be emitted. The valid range is 23 to 32767.
MaxInterrupt INT 20 ms The maximum time which a digit may be interrupted before it is deemed ended. Usually range is between 10ms to 50 ms.

General Tone Parameters

Parm Name Type Default Units Description
OffQualTime INT 500 ms The minimum duration of absence of detected tone before a tone-end event will be emitted. The valid range is 0 to 32767.
OnQualLevel INT -28 dBm The minimum signal level that will be detected. The valid range is –40 to 0.
OnQualTime INT 500 Ms The minimum duration of a detected tone before a tone event will be emitted. The valid range is 22 to 32767.
FREQ1_Parm_1 INT Parameter #1 of the first (or only) frequency of the generated tone. This parameter is computed from the desired frequency.
FREQ1_Parm_2 INT Parameter #2 of the first (or only) frequency of the generated tone. This parameter is computed from the desired frequency.
FREQ1_Parm_3 INT Parameter #3 of the first (or only) frequency of the generated tone. This parameter is computed from the desired frequency.
FREQ1_Parm_4 INT Parameter #4 of the first (or only) frequency of the generated tone. This parameter is computed from the desired frequency.
FREQ2_Parm_1 INT Parameter #1 of the 2nd frequency of the generated tone. This parameter is computed from the desired frequency.
FREQ2_Parm_2 INT Parameter #2 of the 2nd frequency of the generated tone. This parameter is computed from the desired frequency.
FREQ2_Parm_3 INT Parameter #3 of the 2nd frequency of the generated tone. This parameter is computed from the desired frequency.
FREQ2_Parm_4 INT Parameter #4 of the 2nd frequency of the generated tone. This parameter is computed from the desired frequency.
Bandwidth1 INT 70 Hz The bandwidth of the 1st frequency.
Bandwidth2 INT 70 Hz The bandwidth of the 2nd frequency.

Tone-generation has a wait-for-dial-tone capability and the following performance specifications:

Frequency resolution +/-1 Hz
Dynamic level -33 dBm to 0 dBm (programmable), -9 dBm nominal
DTMF digits 0-9, *, #, and ABCD per ITU-T Q.23 and Q.24
DTMF Rate 10 digits/sec (programmable)
MF digits 0-9, KP, ST, STP, KP2/STP2, and ST3 per US(R1) and ITU-T Q.321 European MFC/R2 forward/reverse tones per ITU-T Q.441
Generic tone type Single or dual
Duration 10 msec increments
Generic tone freq. Range 200 to 4000 Hz

DTMF Detection

Dynamic Range -35 to -3 dbm
Minimum tone duration As specified in Q.24; AT&T: 40 ms
Inter-digit timing Detects like digits with a 40 ms inter-digit delay. Detects different digits with 0 ms inter-digit delay.
Acceptable Twist As specified in Q.24; AT&T: +4 dB to –8 dB
Talkoff No hits on the Mitel or Bellcore test tapes
SNR 10 dB (reference to lowest amplitude tone)
Frequency Tolerance As specified in Q.24; AT&T: +/-1.5%< BW < +/-3.5%

MF Signaling Detection

Dynamic Range -35 to -3 dbm
Acceptable Twist 6 dB
Talkoff TBD
Bandwidth +/2% Hz

Test Results

The Commetrex DTMF detector uses a windowing algorithm to meet all the frequency-tolerance requirements of Q.24. The following table contains the test results.

Decode Tests(All digits detected)
Frequency Tolerance Tests Frequency Pos Deviation Neg Deviation
697 2.00% -2.20%
Low Band 770 2.00% -2.00%
852 2.10% -2.00%
941 2.00% -2.30%
1209 2.50% -2.70%
High Band 1336 2.50% -2.70%
1477 2.70% -2.80%
1633 2.80% -2.90%
Twist Tests Standard Twist Reverse Twist
Digit 1 3.9 dB 8.0 dB
Digit 5 4.0 dB 8.4 dB
Digit 9 4.0 dB 8.2 dB
Digit D 4.2 dB 7.9 dB
Dynamic Range Test Dynamic Range
Digit 1 29 dB
Guard Time Test Min Pause Time Min Guard Time
Digit 1 Configurable 29.4 ms
Acceptable Signal to Noise Ratio Test
(-24dBV) pass
(-18dBV) pass
(-12dBV) pass
TALK-OFF Test zero hits (pass)

Call-Progress Analysis (CPA) Voice Detection

The voice-begin event is the first voice event generated when the answering party begins speaking. Note that the signal must be above the SilenceLevel for VoiceOnTime milliseconds. The voice-end event is reported after an absence of voice for SilenceLong milliseconds. If voice is detected again after an absence of voice for SilenceShort milliseconds, the voice-end-short event is reported. The voice-end-short event is not generated if voice restarted after a silence less than SilenceShort milliseconds.

This capability allows the application to infer whether the called party answered with a “Hello”, which is 0.4 seconds, or “Hello, thank you for calling Commetrex”, or “Hi, this is Pete and Alice. We’re not here right now…”

CPA Events

Event Name(ID) Description
CP_BEG CPA Started
CP_BUSY Busy tone detected
CP_CED Modem tone detected
CP_DIALTONE Dial tone detected
CP_END Call progress has completed
CP_NOANSWER No answer (after ringing) detected
CP_RBTONE Ring back tone detected
CP_ROTONE Reorder (fast busy) tone detected
CP_SIT SIT detected
CP_VOICE Voice detected
CP_VOICE_END_SHORT Silence longer than SilenceShort has been detected after detection of voice
CP_VOICE_END Silence longer than SilenceLong has been detected after detection of voice
CP_RBQUIT Ring back quit

Configuration Information

PowerCall adds signal generation-detection and in-band call-progress analysis to an OTF system, giving the system the capability of placing outbound calls over the PSTN and generating and detecting network and general tones. PowerVox adds terminating voice to an OTF-based system, and PowerFax adds terminating fax. All members of the MSP line of DSP-resource boards are supported, as is the all-IP BladeWare IP media server.

OTF for MSP SDK, PN 20070
OTF PowerCall SDK, PN 20050
OTF PowerVox SDK, PN 20060
OTF PowerFax SDK, PN 20030
PowerCall Runtime License, PN 50005

CPA Parameters

Parameter
Name
Default Units Description
SilenceLevel -40 DBm The average value of the input stream below which the signal is considered to be silence (noise). Valid range is –46 to –34.
SilenceTime 500 Msec The minimum length if a silence period after voice is detected to qualify VOICE_OFF. Signal Detection circuit responds to loss of carrier within 4 –5 ms, so minimum value for parameter is 5 ms.
SilenceShort 1000 Msec The time voice must be OFF before sending VOICE_END_SHORT event. This parameter must be greater than SilenceTime. Note that the MSP App must take into account that voice had been off for a duration SilenceTime.
SilenceLong 1500 Msec The time voice must be OFF before sending VOICE_END event. This parameter must be greater than SilenceShort. Note that the MSP App. must take into account that voice had been off for a duration SilenceTime.
VoiceOnTime 50 Msec The minimum length of time voice must be detected before call progress reports a voice begin event.
RB_Max 3000 Msec The maximum duration of a Ring-Back (RB) tone to distinguish it from dial tone. Most RB tones are between 1-2 seconds in duration. The default should be at least 2.5 Sec. The longer it is the longer it takes to qualify dial tone. The shorter it is the more likely it will have to be tuned in the field.
RB_Count 5 Count The number of RB tones to report “No Answer”
RB_StopPeriod 5000 Msec The time from the end of the last RB tone before declaring RB stopped, meaning the called terminal is off-hook without voice, CED or SIT. Few RB tone-off times are greater than 4 seconds; CED period is 3.5 sec
BZ_Max 1500 Msec The maximum period (on time plus off time) to differentiate between slow busy and RB. Busy typically has a period of one second and a 50% duty cycle. A value of 1.5 seconds for this parameter will yield excellent worldwide results
RO_Max 700 Msec The maximum period (on time plus off time) to differentiate between Slow Busy and Fast Busy (reorder). A default value of 700 – 750 msec. will yield acceptable results.
BZ_Count 4 Count The number of Busy tones to qualify “Busy” or “Fast Busy”.
TimeOut 10000 Msec The maximum time that can elapse with no response from the network before call progress stops with a reason of timeout.
StopMask 0x21 Mask Mask to control which events cause call progress to stop. A value may be formed by Oring any of the following:
0x0001 voice begin
0x0002 voice end short
0x0004 voice end
0x0008 modem tone (CED)
0x0010 SIT tone
CPA always terminates if the following are detected: dial tone, busy, and no answer.
PrecMask 3 Mask Mask to control which precise detector to run. A value may be formed by ORing any of the following:
0x0001 CED tone (modem)
0x0002 SIT