Omni 56K USB Lite
Specifications and Functional Description
3-9
3.3.2 Fax Function
Fax Physical Layer Protocol
Table 3-6 Fax Physical Layer Capacity
STANDARD
BIT RATE
[BPS]
BAUD RATE
[BAUD]
MODULATION
CARRIER FREQUENCY
[HZ]
V.17
14400-7200
2400
TCM
1800
V.29
9600-4800
2400
QAM/DPSK
1700
V.27ter
4800-2400
1600/1200
PSK/DPSK
1800
EIA (Electronic Industries Association) Class 1 Command Set
Please refer to
Fax Command Set
in Chapter 5.
ITU-T T.30 Fax Protocol
The ITU-T T.30 fax protocol is known as the G3 fax handshake signals and procedures. The modem takes
full control of this protocol - initiating and terminating fax calls, managing the communication session, and
transporting the image data. Therefore, the modem relieves the computer fax software of the T.30 protocol
handling.
Your modem allows for fax speeds up to 14400 bps when transmitting to a fax machine which complies with
the V.17 fax standard. Speeds fall back to 12000, 9600, or 7200 bps in poor line conditions. When
connecting to a G3 fax device, your modem allows for fax speeds up to 9600 bps and automatically falls
back to 7200, 4800, and 2400 bps if the line quality is poor.
3.3.3 Voice Function
Voice capability stands for the modem's ability to digitize incoming voice messages, which the computer
stores and forwards. It also means that the modem can playback the recorded digitized voice on line for a
message announcement.
Voice IS-101 Command Set
Please refer to the
Voice command
sets in Chapter 5.
4-bit Voice Data Compression
The main issue in the digitized voice mode is the amount of storage required. A relatively simple ADPCM
algorithm can reduce the speech data rate to half the rate and maintain about the same voice quality. This
algorithm can also be used to reduce the speech data rate to 1/3 or 1/4 of the original rate, but with voice
quality degradation. Only 4-bit ADPCM is used in the Omni 56K USB Lite.
