V.27ter Fax Software

VOCAL’s V.27ter Fax Software implements ITU-T V.27ter which defines the modulation methods and operating sequences for a 4800/2400 bps duplex modem designed for use on connections set up by switching in the general telephone network. Data transmission is at 4.8 kbps, with a fallback rate of 2.4 kbps, with symbol rates of either 1200 or 1600 symbols per second.

Software developers can control all of the V.27ter facsimile modulations and data streams with VOCAL’s T.30 library or with VOCAL’s facsimile service Class 1 Command Set(EIA-578 and T.31). The T.30 library could in turn be controlled by VOCAL’s facsimile service Class 2 Command Sets T.32 (Fax Class 2.1), EIA-592 (Fax Class 2.0), or industry standard (Fax Class 2). With Fax Class 1, most of the protocol is executed in software, with the advantage that any changes don’t require hardware modifications. This is in contrast to Fax Class 2, where image processing is handled by the modem.

The line interface for the V.27ter fax software may be an analog front end (codec and DAA) or a digital interface such as T1/E1, Switched 56, and ISDN. The upper end of this software offers a direct binary and HDLC interface.

Features

• Fully compliant with ITU recommendations
• Modular software suite available with controller code
• Optimized for high performance on leading edge DSP architectures
• Multi-tasking environment compatible
• Multichannel implementation

Configurations

• DAA interface using linear codec at 7.2 kHz, 8.0 kHz or 16.0 kHz sample rate
• Direct interface to 8.0 kHz PCM data stream (A-law or μ-law)
• North American and International Dialing/Telephony dialing functions available
• Facsimile protocol layer (T.30 with ECM/BFT) available
• Facsimile service class 1 command sets (T.31 and EIA-578) available
• Facsimile service class 2 command sets (T.32, EIA-592 and industry standard fax class 2) available.
• System can be combined with V.34fax facsimile modulations and startup procedures (V.8 and V.8bis).