Intel 537EX - Manual (Page 80)

80 536EX Chipset Developer’s Manual
Intel Confidential
IS-101 Voice Mode AT Commands
+VSM=m
manufac-
turer-
specified
Compression Method Selection: This command contains four parameters that specify the voice
compression method, voice sampling rate, silence compression sensitivity, and the degree of silence
expansion. The DCE can support different capabilities for each compression method.
m= , , ,
Defaults: m = 140, 8000, 0, 0
Compression Method: This parameter selects a voice compression method. The DTE can
obtain the label and a string constant identifier by using the +VSM? command.
Range: 0–2, 128, 129, 132, 140, 141
0 LIN1: 8-bit Linear PCM (pulse code modulation) sampling using twos-complement
signed numbers
1 LIN2: 16-bit Linear PCM sampling using unsigned numbers
2 AD4: 4-bit Adaptive differential pulse code modulation
128 LIN1: 8-bit Linear PCM (pulse code modulation) sampling using twos-complement
signed numbers
129 LIN2: 16-bit Linear PCM sampling using unsigned numbers
132 AD4: 4-bit Adaptive differential pulse code modulation
140* CL1: 8-bit Intel A-law
141 AD3: 3-bit Adaptive differential pulse code modulation
Sampling Rate: This parameter selects the DCE voice sampling/digitizing rate for the voice
signal. The supported sampling rates are dependent on the compression schemes used. Use the
+VSM=? command to obtain supported sampling rates.
Range: 4800, 7200, 8000, and 11025 samples/second
4800 Default used by previous Intel modems
7200
8000* Used by some bulletin boards
9600
11025 Used by many Windows* WAV files
Silence Sensitivity: The function of this parameter depends on whether the DTE is
transmitting or receiving in voice mode. The DTE can modify the silence expansion using the
parameter. When transmitting voice, a non-zero value of this parameter informs the DCE that the data
stream was recorded with silence compression.
Transmission: Range: 0
0* Disabled
When receiving voice, this parameter changes the level of noise that the DCE treats as silence. A
higher ‘n’ number raises the threshold of noise detection.
Reception: Range: 0
0* Disables DCE silence compression
increments of 1 Raises noise detection threshold
Table 25. Voice Mode Command Descriptions (Continued)
Command Default Description
NOTE: An asterisk (*) denotes the factory-default setting.