SA541 Sames, SA541 Datasheet - Page 11

• Manufacturer Part Number: SA541
• Description: PULSE/DTMF SWITCHABLE DIALLERS
• Manufacturer: Sames

SA541
DTMF Tone Filtering
Figure 3: 2-Pole Sallen and Key Filter Circuit
9.
DTMF Dialling (Figure 4)
During DTMF dialling, the MUTE output goes to logic ‘1’ and remains there for the
duration of the tone transmission. The IMP output remains low during tone
transmission. The MF OUT output rises to its d.c. level of 0,9 V
at the start of the
DD
tone transmission and is kept there between tone bursts. This is to avoid transients
at the beginning and end of tone bursts.
The maximum rate at which tones are sent to line is 100ms on, followed by 100ms
off. If keys are activated faster than this, they are placed in a temporary store and
then sent to line at the maximum rate. Dialling from the LNR store occurs at the
maximum rate.
If a key is held down for longer than 100ms, the tone output will continue until the
key is released.
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