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Chapter 4 – Voice Commands
Multi-Tech Systems, Inc. SocketModem MT5634SMIxx Reference Guide (S000263C) 106
Command: +FCLASS=8 DTMF Detect Detect and Control DTMF
Values: 8 characters, case sensitive
Description: The +FCLASS=8 is used to detect and control DTMF using the procedure below:
1. Enter the command AT+FCLASS=8 <cr> to the modem.
2. Call into modem with phone. A
¾r (incoming ring indication) is displayed, followed by
OK. The modem is now in Online Voice Command mode, allowing DTMF characters
to be passed through from the remote phone. The characters are displayed as shown
below:
AT+FCLASS=8
OK
¾R is Ring
¾/¾1¾1¾~
The Data link escape character (
¾), and the ‘start of DTMF tone shielding’ character (¤)
are both output once a button is pressed. The DTMF digit will continue to be output along
with a
¾ until the button is released. Then another ¾ is output along with a ‘DTMF
transitions to off’ (~) character. Silence on the line is indicated with a (
¾s) displayed.
DTMF (dual tone multi frequency) is the signal to the phone company that you generate
when you press an ordinary telephone’s touch keys. DTMF has generally replaced loop
disconnect (“pulse” or “rotary”) dialing. With DTMF, each key you press on your phone
generates two tones of specific frequencies. So that a voice can’t imitate the tones, one
tone is generated from a high-frequency group of tones and the other from a low
frequency group.
Touch Tone Signals
Digit
Low frequency High frequency
1 697 Hz 1209 Hz
2 697 1336
3 697 1477
4 770 1209
5 770 1336
6 770 1477
7 852 1209
8 852 1336
9 852 1477
0 941 1336
* 941 1209
# 941 1477
When any key is pressed, both the high and low tones of the row are generated, hence
the name “dual tone”. For example, pressing the ‘5’ button generates the tones 770Hz
and 1336Hz. The frequencies were chosen to avoid harmonics (no frequency is a
multiple of another, the difference between any two frequencies does not equal any of the
frequencies, and the sum of any two frequencies does not equal any of the frequencies).
For additional information on DTMF, see the Telecommunications Industry Association’s
Web site at http://www.tiaonline.org/resources/other_links.cfm.
Command: AT+FCLASS=? <Enter> Display Service Class Capabilities
Values: 0, 1 (other values are reserved)
Default: 0
Result Codes: OK if the command is accepted; ERROR if the parameter value is out of range.
Description: The +FCLASS=? command displays the set of Service Classes supported by the
modem from the list of values (e.g., 0,1 for a modem that supports data comm plus fax
Service Class 1). This command returns the service class or classes available with the
modem. The modem returns a list of all supported values, separated by commas if more
than one class is supported. For example, a modem that supports data communications,
Class 1 Fax, Class 2 Fax, and Voice mode functions would respond with "0,1, 2.0, 8".