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FarSync Flex V3 – The Synchronous / Asynchronous USB Adapter

FarSync flex USB 620wide

The FarSync Flex V3 USB adapter has been developed to provide high performance sync communications support for Linux and Windows systems.

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The FarSync Flex V3* USB adapter is a high quality synchronous solution for business, government and military applications, using the FarSite customisable communications controller it has been developed
to provide a high performance, neat, durable and versatile connectivity for Linux and Windows systems.

The bus powered USB adapter will support a synchronous line at
speeds of well over 3 Mbits/s continuous. The highly flexible universal network connector supports
RS530 (RS422 signaling)
, RS449 , RS485 and
network interfaces.

The adapter can support the host computer’s TCP/IP protocol stack or an Application can be written to use the low level API for a variety of different functions. The FarSync Flex SDK provides a Developers Toolkit for the product.

The Flex can be used for line monitoring with the addition of a special Monitor cable. A monitoring application is included. The monitoring support is also compatible with Wireshark.

The FarSync Flex supports PC connections to secure BRENT units using an X.21 connection.

For DAB connections the FarSync Flex supports ETI (NI, V.11) and STI (PI, V.11).

*The FarSync Flex V3 superseded the FarSync Flex V2 in July 2018, it is a plug in replacement. The Flex V3 is 100% compatible (updated driver required) with the additional features of a wider operating temperature range and higher operating speed. The FarSync Flex V2 is no longer available due to part obsolescence.

Typical Applications

The FarSync Flex adapters are suitable for a very wide range of uses. Typical applications include:

  • HDLC framing support for non standard or specialist protocols
  • Interfacing to transparent bitstreams for handling unusual protocols
  • Line monitoring (both transmit and receive)
  • Data generator for test systems
  • Engineering monitoring and for control of systems
  • Master or slave in a RS485 2 or 4 wire multidrop environment
  • Connection to radio modems controlling data rate using dynamically variable clock speeds
  • Interfacing video and voice bitstreams such as T-DMB, DAB ETI (N1, V.11)  and STI (P1, V.11)

FarSync Flex – Product Details

The FarSync Flex is supplied with support for Windows and Linux. This includes a low level driver that allows access to the communications features available in the hardware and an optionally installable driver that connects with the standard TCP/IP protocol stack to allow access to IP based networks such as the Internet. Multiple devices can be installed.

Key Features

The intelligent FarSync Flex is designed for reliability, high performance and flexibility. The adapter uses a fast ARM processor with Flash and RAM for the onboard code.

  • Network interfaces for  X.21
    , V.35, RS232
    (V.24, X.21bis)
    , RS449, RS530
    (EIA530, RS422),
    and RS485.
  • Sync line speeds over 3 Mbits/s, Async line speeds up to 115.2 Kbits/s
  • USB 2.0 high-speed mode (480mb/s), USB 3.0 and 1.1 compatible
  • Multiple Flex operation from a single server
  • High efficiency USB Bus powered, energy saving design
  • NRZI, NRZ, Manchester Encoding, Conditioned Di-phase, FM0 and FM1 line signaling formats, tri-state transmitters and receivers
  • Master of slave in 2 or 4 wire multidrop (NRZI, Manchester Encoding, Conditioned Di-phase, FM0 or FM1) RS485 operation
  • Line clocking external or internal for 100’s of synthesizer generated clock speeds with fully configurable bidirectional clocking
  • Custom clock rates configurable dynamically through the API with glitch free transition between rates
  • Dual bank flash for secure in field upgrades and previous system restore capability
  • Software selectable Synchronous HDLC, Transparent Bitstream and Asynchronous formats
  • FarSite customisable communications controller
  • New releases of the software available for free download
    from the Download page in this web sites Support section
  • Optional mounting brackets (factory fitted)
  • Board only and blank case options for OEM requirements

Key Features supported on Linux

The Char I/O API provides a programming language independent, high-level interface to the FarSync base driver it supports access to bit synchronous (HDLC) framed and transparent bitstream data.

The card can also use the TCP/IP stack to allow access to IP based networks such as the Internet. It also allows selection of the full range of clock modes.

The link level protocol used can be PPP, Cisco HDLC, LAPB (using hdlcX API) or Frame Relay with optional authentication by CHAP, MSCHAP or PAP (RFC 1334) thus providing a standard point-to-point network interface. ETI (NI, V.11) is supported with the FarSync SDK.

The card installs seamlessly as a plug and play device. The driver supports Linux kernel versions from 2.6 and later including the leading distributions supplied by Redhat, SuSE, CentOS, Debian, Ubuntu, Fedora, Slackware and more. Multi-processor systems are supported. The driver is dynamically loadable so a kernel rebuild is not required for the driver to be installed.

FarSite is committed to supporting the cards on new versions of Linux and Linux kernels as they are released. The source code for the driver is supplied with the product allowing rebuilding by the end user for use with almost any of the current or future Linux variants. The driver supports both little endian and big endian memory storage formats.

A configuration utility is provided to set the line speed, interface type and protocol, after which the ports may be configured with standard networking tools.

Key Features supported on Windows

The FarSync Flex supports a Windows based API, common to the entire range of FarSync cards/devices, it is referred to as the FarSync Windows API (FsWinAPI). This is an extension of the MS Win32 COMM API and enables, for example, applications developed to support COM ports, to be easily ported to use FarSync support in synchronous modes. This standardization enables the API to also be readily accessible from higher level environments such as .NET, C#, VB etc. Standard COM port access is provided for use in Async mode.

The FsWinAPI provides applications with direct access to the adapter’s communications port/s for bit sync (HDLC) framing, LAPB, V.120, ETI (NI, V.11) and also transparent bitstream operation for video and voice type applications.

The FarSync Flex can also be installed to appear as a NDIS (LAN) interface so it can simply use the TCP/IP stack over PPP to allow access to IP based networks such as the Internet.

LabVIEW applications can access this card.

The product is supplied with a comprehensive configuration utility. The lines can be reconfigured and restarted without reloading the software. There is context sensitive help and an on-line manual should it be required. An advanced tab permits users to further specify the configuration of the line if necessary.

The product is supplied with its own Line Monitor that allows the user to record, display and store line traffic with WAN protocol decoding for fast debugging. The Line Monitor application is also suitable for standalone use with a special cable. The line monitor function is compatible with Wireshark via a DLL supplied with the Flex.

FarSync Flex SDK – The Developers Toolkit

The SDK includes support for writing applications on both Linux and Windows and contains documentation, working sample applications, development and test utility applications. There is everything a user needs to rapidly develop and test a wide variety of applications such as specialist synchronous (HDLC framed) protocols or transparent bitstream data requirements including Audio, MPEG Video T-DMB and DAB ETI and STI with bitstream encoder and decoders. Also included are details on using the Flex with RS485 networks.

The FarSync SDK is ordered separately from the FarSync Flex.

Our Engineering department provides free email and telephone assistance to application developers using the API as part of the package provided when the FarSync SDK is purchased.

See details on the FarSync SDK Developers Toolkit and the APIs supported.




For Windows configuration is by a GUI application, a typical screen is shown on the right.

The line can be reconfigured and restarted without reloading the software.

There is context sensitive help and an on-line manual should it be required. An advanced tab permits users to exactly specify the configuration of the line if necessary.

For Linux a configuration utility is provided, alternatively text files can be used.


FarSync Flex – Software Technical Specifications
Distribution Support Distributions by Red Hat, SuSE, Slackware, Mandriva, Ubuntu, Debian, Fedora and more.
Drivers for kernel versions from 2.6 and later on both single and multi-core 32 and 64 bit systems.
Kernel Support Sub versions of kernel releases from 2.6.12 and later.
Big Endian and Little Endian memory storage format drivers supplied.
Protocol Supported TCP/IP, PPP, Cisco HDLC, LAPB, Frame Relay, CHAP, MSCHAP, PAP (RFCs 1661, 1332, 1334). Bitstream. ETI (NI, V.11) with the FarSync SDK.
API and Interfaces Char I/O API, hdlcX.
O/S Types Windows 10, 8, 7, Vista, Windows Server 2016, 2012 and 2008, LabVIEW running on a Windows O/S.
32 and 64 bit (single and multi-core systems)
Protocol Supported TCP/IP, PPP, LAPB, V.120, CHAP, PAP (RFCs 1661, 1332, 1334), ETI (NI, V.11), Bitstream.
API and Interfaces FsWinAPI, NDIS (LAN) where the line appears as a LAN interface
Utilities Line Monitor to record, display and store line traffic included, Wireshark compatible

FarSync Flex – Hardware Technical Specifications
General Intelligent USB adapter with ARM processor, dedicated RAM and dual bank Flash memory,
Field upgradeable onboard firmware,
USB bus powered, USB 2.0 (high-speed – 480mb/s mode) 3.0 and 1.1 compatible,
Network line connector: HD26 for connection of network cables
Physical characteristics Size: – Height 30mm, Length 126 mm, Width 62mm
Weight: 190g
0.6 metre A to B USB cable with thumb screw secured B connector.
Network connections supported
X.21 (V.11)
– DTE  DB15M connector,,

– DTE MRAC-34 (V.35M) connector,

RS232 (V.24, X.21bis)
– DTE DB25M connector,

RS530 (RS422)
– DTE  DB25M connector,
RS449 – DTE  DB37M connector,
RS485 2 and 4 wire,
DCE type cables are also available
Link speed range RS232: up to 128 Kbits/s
X.21, V.35, RS530, RS449, RS422, RS485: to well over 3 Mbits/s
Sync and Async Synchronous operation to well over 3 MBits/s,
Asynchronous operation up to 115.2 KBits/s
Line Signal Modes NRZ, NRZI, FM0, FM1, Manchester Encoding and Conditioned Di-phase to well over 3 Mbits/s
ESD protection Yes, Littelfuse high speed ESD and over-voltage
Indicators LED displaying network line status
Approvals EN55022 class B, CE,
FCC class B
Power requirements USB Bus powered, < 500 mA on full load, < 2 watt
MTBF MTBF: 360,181 hours – calculation based on Bellcore Method 1 Case 3, 40°C ambient, 15°C case temperature rise above ambient.
Operating Temperature Range –40°C to 85°C ambient air temperature. (industrial temperature range)
Line clocking
Internal and externally generated line clocking is supported,
Internal clock range 75 baud to 4.096 Mbits/s on X.21, V.35, RS530, RS422, RS449 and RS485,
Internal clock range 75 baud to 128 Kbits/s on RS232 (V.24),
Custom clock rates are dynamically configurable through the API with glitch free transitions.
Extra Line Control Bit reversal, receive clock inversion, configurable resistive interface signal termination.
Full configurable bidirectional clocking.
Cable type compatibility Cables are ordered separately see list of
cables available
Warranty 5 years
RoHS2 Compliant Yes

Download the FarSync Flex Hardware Manual

Order Information
Product Name Photo Description Product Code
FarSync Flex V3 FarSync Flex 1 port synchronous USB Adapter with Linux and Windows software. This is the base product, it includes the Flex hardware, USB cable, drivers, utility programs, documentation on CD-ROM and a quick start guide. * FS4100
FarSync SDK The Linux and Windows Developers Toolkit for the FarSync Flex – required if you want to write software to use the adapters API FS9610
FarSync Flex X25 Supports all the features of the FarSync Flex plus X.25 support and an X.25 SDK * FS6100
FarSync BERT BERT line test software for use with the FarSync Flex on Windows FS9509
* If you require the FarSync Flex for use with Nokia Siemens Networks LMT software then please contact us.
Cable Options
KCR1 Cable KCR1 RS232 (V.24, X.21bis) and RS530 (EIA530, RS422) DTE cable. DB25M connector, same cable for both interfaces, 1.5 metres FS6011
KCR1-DCE RS232 (V.24, X.21bis) and RS530 (EIA530, RS422) DCE cable. DB25F connector, Same cable for both interfaces, 2 metres FS6070
UCX1 Cable UCX1 100x31 X.21 (V.11) DTE cable. DB15M connector, 1.5 metres FS6062
UCX1-DCE X.21 (V.11) DCE cable. DB15F, 2 metres FS6075
UCV1 Cable UCV1 100x28 V.35 DTE cable. MRAC-34 (V.35M) connector, 1.5 metres FS6063
UX35C Cable UX35C 100x31 V.35 DCE cable. MRAC-34 (V.35F) connector, 1.5 metres. FS6095
KC449 RS449 (RS422) DTE cable. DB37M connector, 1.5 metres FS6019
KCR-MON KCR-MON Monitor Cable – RS232 (V.24) and RS530 (RS422, EIA530) with DB25M to DB25F passthrough, 1.5 metres FS6016
KCX-MON KCX-MON Monitor Cable – X.21 (V.11) with DB15M to DB15F passthrough, 1.5 metres FS6017
Flex Mounting Kit Flex brackets A pair of FarSync Flex mounting brackets.
Must be ordered with the FarSync Flex, factory fitted.
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