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VFT product family

The VFT family consists of various VFT boards which are based on the binary frequency shift keying (FSK) transmission procedure. This is a very robust system with a good track record for transmitting mission-critical data via copper wire. All VFT boards have one common denominator: fully transparent transmission of a serial incoming signal. In other words, parameterising baud rates, start and stop bits, as well as parity, is not necessary.

Selective VFT is based on signal-processor technology. With digital filters it implements bandlimiting transmission channels compliant with IT-CCITT for transmission rates of 50 to 2400 bps in the 300-3400 Hz voice band. In this case several channels can be flexibly placed in the frequency multiplexer, so that a line of several VFT boards can be used at the same time.

SWT is a new generation of conventional VFT boards that is aiming for faster data rates. It allows the operation of a multidrop VFT party line modem to telecontrol lines with a variety of staggered tributary stations with a permanent transmission channel and without any complex filtering. The SWT board is available for up to 9600 bps and as a V.23 modem for up to 1200 bps.

As a cost-effective board with top-hat-rail assembly, the SWT board has been designed to transmit on 2-wire and 4-wire copper lines. It’s particularly ideal when advanced transmission networks, such as TCP/IP networks with protocols like IEC 60870-5-101 or 104, have to integrate existing telecontrol lines with staggered tributary stations. A 2-wire plug-on module for assembly in customers’ own devices is also available.

Our offering

  • Traditional telecontrol applications, telecontrol channels in frequency division multiplexing
  • Supports data volumes in the IEC 60870-5-101 protocol
  • Identifies figures in meters in residential and industrial buildings
  • A replacement for VFT devices, compliant with ITU-T V.23

WT 2400

  • A selective VFT device 50 … 2400 bps
  • All functions are software-based with one piece of hardware for all channels
  • No termination hybrid, no levelling necessary and easy to commission based on the table
  • A high level of selectivity, low isochronous distortion, precorrector integrated


  • Super VFT for 9600 bps and 20 km @ 0.8 mm line diameter
  • Alternatively V.23 with 1200 bps and 30 km @ 0.8 mm line diameter
  • Cost-effective solution in a top-hat-rail body


  • Super VFT for 9600 bit/s and 20 km @ 0.8 mm line diameter
  • Alternatively V.23 for 1200 bit/s and 30 km @ 0.8 mm line diameter
  • Compact two-wire module 6 x 9 cm for assembly in customers’ devices
power plant engineer for substation

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