V.27 Fax Modem SoftwareV.27ter fax software provides a 4800/2400 bps duplex modem for use in the general telephone network. V.27 fax is available as a real-time implementation with support for multichannel applications. The V.27ter fax libraries are modular and can be executed by developers as a single task under a variety of operating systems or standalone with its own microkernel. Contact us to discuss your V.27 fax software application requirements.

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VOCAL’s V.27ter fax software is optimized for conventional processors and DSPs from ADI, ARM, Intel, TI and other vendors. Our V.27ter fax software may be licensed as a standalone algorithm, a library, or complete design with custom solutions available.

V.27ter Fax Software Features

V.27ter Fax

ITU-T V.27ter Fax 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.




VOCAL’s optimized fax software is available for the following platforms. Please contact us for specific V.27ter fax supported platforms.

ProcessorsOperating Systems
  • Texas Instruments – C6000 (TMS320C62x, TMS320C64x, TMS320C645x, TMS320C66x, TMS320C67x), DaVinci, OMAP, C5000 (TMS320C54x, TMS320C55x)
  • Analog Devices – Blackfin, ADSP-21xx, TigerSHARC, SHARC
  • PowerPC
  • MIPS – MIPS32, MIPS64, MIPS4Kc
  • ARM – ARM7, ARM9, ARM9E, ARM10E, ARM11, StrongARM, ARM Cortex-A8, Cortex-M1
  • Intel / AMD – x86, x64 (both 32 and 64 bit modes)
  • Google Android
  • Apple iOS / iPhone / iPad & MacOS
  • Unix,  Linux, μClinux, BSD
  • Microsoft Windows ACM / RTC / CE / Mobile
  • Symbian
  • eCOS / eCOSPro
  • Wind River VxWorks
  • Green Hills Integrity
  • Micrium μCOS