CMX867D2(2000) View Datasheet(PDF) - CML Microsystems Plc

Part Name

Description

Manufacturer

CMX867D2
(Rev.:2000)

Low Power V.22 Modem

CML Microsystems Plc 

Low Power V.22 Modem

CMX867

1.5.6 Rx DTMF/Tones Detectors

In Rx Tones Detect mode the received signal, after passing through the Rx Gain Control block, is fed to the

DTMF / Tones / Call Progress / Answer Tone detector. The user may select any of four separate detectors:

The DTMF detector detects standard DTMF signals. A valid DTMF signal will set bit 5 of the Status Register to

1 for as long as the signal is detected.

The programmable tone pair detector includes two separate tone detectors (see Figure 11). The first detector

will set bit 6 of the Status Register for as long as a valid signal is detected, the second detector sets bit 7, and

bit 10 of the Status Register will be set when both tones are detected.

The Call Progress detector measures the amplitude of the signal at the output of a 275 - 665 Hz bandpass

filter and sets bit 10 of the Status Register to 1 when the signal level exceeds the measurement threshold.

10

0

-10

-20

dB

-30

-40

-50

-60

0

0.5

1

1.5

2

2.5

3

3.5

4

kHz

Figure 6a Response of Call Progress Filter

The Answer Tone detector measures both amplitude and frequency of the received signal and sets bit 6 or bit

7 of the Status Register when a valid 2225Hz or 2100Hz signal is received.

© 2000 Consumer Microcircuits Limited

13

D/867/1

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