User's Manual

page 17/51
HiAll
NC
User Manual 2012/06/28
Distortion 5% max at 1K Hz, nominal input power
3.3.1.3 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 guaranteed 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 on the GSM
network provider. SAGEMCOM does not guarantee any success on using this function.
However tests on HiAll
NC
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.
3.3.2 Digital PCM Audio
The HiAll
NC
module features a PCM interface. The PCM interface is a high speed full duplex interface that can
be used to send and receive digital audio data to external audio ICs.The HiAll
NC
PCM interface is highly
configurable:
- PCM master or slave mode
- 8bits or 16 bits data word length
- MSB or LSB first
- Rising or falling sampling clock edge
- Configurable PCM bit clock rate up to 1MHz
Signals Module connector pin
number
Description
PCM_CLK 21 Clock
PCM_IN 66 Digital audio input
PCM_OUT 65 Digital audio output
PCM_SYNC 22 Audio signal frame synchronization