User's Manual

page 16/64

Note d’étude / Technical document : URD1– OTL

5665.3

– 003 / 72238 Edition 01

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4.2.3 DTMF OVER GSM NETWORK

Former systems used to transmits data through DTMF modulation on RTC telephone lines.

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Audio DTMF tones are not guarantee over GSM network

This is due to the nature of the GSM Voice CODEC - it is specifically designed for the human voice and does

not faithfully transmit DTMF.

When you press the buttons on your GSM handset during a call, this goes in the Signalling channel - it does not

generate in-band DTMF; the actual DTMF tones are generated in the network.

Therefore if your design needs the DTMF functionality, you should know their transmission over the network is

not at all guaranteed (because of voice codec). This could work or fail depending very strongly to the GSM

network provider. SAGEMCOM does not guarantee any success on using this function.

However tests on HiLoNC V2 shown this feature can work on some GSM Networks. Successful transmissions

and receptions have been done with 300ms of characters duration and 200mVpp as input level on microphone

input.

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If this function is needed, first try with your network and those parameters then (if success) try to tune

them to fit your specification.

4.3 PWM

4.3.1 PWM outputs

The HiLoNC V2 module can manage two PWM outputs.

They can be configured with appropriate AT command (for more details refer to AT command set for

SAGEMCOM HiLoNC V2 module specification).

User application can set for each output:

• Frequency between : 25.6KHz and 1083.3KHz

• Duty range from: 0 to 100%

4.3.2 PWM for Buzzer connection

The HiLoNC V2 module can manage a dedicate PWM output to drive a buzzer. The buzzer can be used to

alarm for abnormal state.

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Resistors should be added to protect the buzzer. The value of these resistors depends on the buzzer and

the transistor. Normally, they can be set as 1KΩ.

Figure 11: Buzzer connection

HiloNC

VBAT

PWM2