Z02215
Single Chip Modem with Integrated Controller, Data Pump, and AFE
22
Table 3. AT Command Set (Continued)
Function and Description
Command
#F
DTMF
Detection
Command
#F is used to detect DTMF digits received by the modem when it is off-hook in
the COMMAND state. #F does not operate during a data connection. The #F
command can only be entered from the command state and assumes that the
phone is off-hook. For example, to dial a call and then immediately enter the
DTMF detection mode the following series of steps are taken:
1. Send ATDxxxxx; command where xxxxxis the phone number.
2. Wait for the OKresponse.
3. Send AT#F1to the modem.
4. You are now in the DTMF detection mode.
During DTMF detection the modem decodes received DTMF tones and issues
a line of ASCII text to the terminal each time a DTMF digit is detected.
DTMF Digit
Output Text
0–9
*
0–9
10
#
11
A–D
12–15
The following table describes the output text according to which pair of DTMF
high and low tones were detected.
High band/
Low band
697 Hz
770 Hz
852 Hz
941 Hz
#F0
1209 Hz 1336 Hz 1477 Hz 1633 Hz
1
2
5
8
0
3
12
13
14
15
4
6
7
9
10
11
Detect DTMF digits with out using a human speech filter.
DTMF digits as short as 50 ms can be detected.
#F1
Detect DTMF digits while using a filter that reduces the
effect of human speech on the detection of DTMF digits,
improving the accuracy of detection. DTMF digits as short
as 60 ms can be detected.
PS001907-0904
AT Command Set
ZILOG [ ZILOG, INC. ]
