ZyXEL Omni 56K USB Lite User Guide - Page 41

Omni 56K USB Lite 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. Specifications and Functional Description 3-9