Leased line modems for industrial applications

this product is only available for special projects. It is not in regular production.


The MuLogic LLM-336FX series are voiceband modems for reliable data communication over 2-wire or 4-wire leased lines at data rates up to 33.6 kbit/s. The LLM-336FX modems are designed for industrial applications and can be powered from any 9 to 36 Volts or 18 to 72Volts power source.

In addition to the LLM-336, the LLM-336FX modem offers full-duplex and swiched carrier operation in V.33, V.29, V.27 and V.23 modes.

 3 versions are available:
  • LLM-336FXD for panel or DIN rail mounting (RS-232C and RS-485 interface)
  • LLM-336FXS for for desktop or shelf use (RS-232C interface. RS-485 optional)
  • LLM-336FXR rack card (RS-232C and RS-485 interface)

All modems support full and half duplex operation modes and can be used on point-to-point and multi-point lines. Special features for SCADA and Modbus RTU communication are implemented.

  • ITU-T modes V.34, V.33, V32bis, V.32, V.29 V.22bis, V.22, V.23 and V.21 for Full-duplex.
  • Full duplex line rates from 300bit/s to 33,6kbit/s
  • ITU-T modes V.29, V.23, V.27 for half duplex and multi-point switched carrier operation.
  • Half duplex line rates from 1200 to 9600 bit/s
  • Asynchronous data rates up to 115.2 kbit/s for buffered or error corrected data
  • Synchronous data rates up to 33,6 kbit/s
  • Transparent asynchronous operation from 0 to 9600 bit/s (point to point operation)
  • Data-controlled carrier for half duplex and multi-point operation. (no need for RTS signal)
  • V.42/MNP2-4 error correction for asynchronous data
  • V.42bis/V.44 data compression for asynchronous data
  • Supports Modbus RTU, Modbus ASCII, DNP3, IEC 60870.5 and more.
  • Isolated supply voltage input (ac and dc) for industrial applications.
  • Supply voltage: 9 to 36Vdc (19 to 26Vac) or 18 to 72Vdc (22 to 50Vac)
  • Din-Rail mounting bracket for LLM-336D
  • Extended temperature range
  • RS-485/422 interface (LLM-336FXD and LLM-336FXR, optional for LLM-336FXS)
  • Operating modes selected by means of Dip switches or customized via serial port.
  • Central modem control for LLM-336FXR in MCF-16.3 rack. (Using CMC-16 card)

Application Areas
Asynchronous applications
For applications with asynchronous data, the LLM-336FX supports a buffered DTE (terminal) interface. The modem accepts data rates from 300 bit/s to 115200 bit/s and supports error correction and data compression according to the V42/V.42bis, V.44 and MNP5 protocols. Both 10 and 11 bits character formats are supported.

For data rates up to 9600 bit/s, the modem can also offer a fully transparent data path. This allows for operating all asynchronous data formats and rates up to 9600 bit/s, without changing the modem configuration.
Synchronous applications
For applications with synchronous data, the LLM-336FX supports data rates from 1200 to 33600 bit/s Synchronous transmit clocking information can be generated by the modem, externally supplied by the DTE, or slaved to the receive clock.
Switched carrier and multi-point/multi-drop applications
The LLM-336FX supports half duplex en 4-wire full duplex with switched carrier operation in V.23, V.27, V.29 and V.33 modes. The modem can be used for multi-point or multi-drop networks on conditioned and unconditioned lines.

Half duplex operation is supported for asynchronous and synchronous data.
For asynchronous data the LLM-336FX offers a buffered interface which enables the DTE to operate at a higher data rate than the modem.

Carrier control is by means of the RTS signal input or controlled by the TxD (transmit data input). See "AutoCarrier".
The LLM-336FX can operate in half duplex switched carrier mode on 2-wire and 4-wire lines.

For multi-drop operation, the modem's line connection can be set to high-impedance while receiving. This allows for a larger amount of modems to be present in one single line and offers a better matching to the line impedance.

Scada and Modbus applications
The LLM-336FX supports SCADA communications such as Modbus RTU, Modbus ASCII, DNP3 and IEC 60870.5.

The modem has a quite unique feature that makes it possible to operate in half duplex and multi-point modes under control of the data signals only.
This allows for RS-232, RS-422 and RS-485 devices (that cannot control the RTS signal) to control the modem carrier just by sending data.

Radio communication
As the LLM-336FX is a voiceband modem, operating in the 100Hz to 4000Hz band, the modem can also be connected to radio systems suitable for voice communication.

The LLM-336FX can be configured by means of DIP switches. 
Over 40 pre-defined operation modes can be selected.
2 user defined operation modes can be stored in non volatile memory.

Power supply
The LLM-336FX modems are equipped with an internal galvanic isolated power supply.
Two voltage ranges are available:
  • 9..36Vdc (19..26Vac)
  • 18..72Vdc (22..50Vac)
For mains power operation (100.240Vac) an external power adapter can be supplied with the modem.

Extended temperature range 
The modem can be used in many environments. It is suitable for operating at ambient temperatures ranging from -25 to +70 C. 
Technical Specifications

Full duplex modulation modes

  • ITU-T V.34; 33k6, 28k8, 26k4, 21k6, 19k2, 14k4, 12k and 9k6 bit/s async/sync.
  • ITU-T V.33; 14k4 and 12kbit/s async/sync.
  • ITU-T V.32bis; 14k4, 12k and 7200 bit/s async/sync.
  • ITU-T V.32; 9600 and 4800 bit/s async/sync.
  • ITU-T V.29; 9600, 7200 and 4800 bit/s async/sync.
  • ITU-T V.27; 4800 and 2400 bit/s async/sync.
  • ITU-T V.22bis; 2400 and 1200 bit/s async/sync.
  • ITU-T V.22; 1200 bit/s async/sync.
  • ITU-T V.23; 1200 bit/s asynchronous.
  • ITU-T V.21; 300 bit/s asynchronous.

Switched carrier and multi-point modulation modes

  • Half-duplex on 2-wire lines. Full-duplex on 4-wire lines.
  • ITU-T V.33; 14k4 and 12k bit/s async/sync.
  • ITU-T V.29; 9600, 7200 and 4800 bit/s async/sync.
  • ITU-T V.27; 4800 and 2400 bit/s async/sync.
  • ITU-T V.23; 1200 bit/s asynchronous.

Error correction and data compression 

  • ITU-T V.42 LAPM error correction
  • MNP2-4 error correction
  • ITU-T V.42bis data compression
  • MNP5 data compression

DTE interface

  • ITU-T V.24/V.28 (EIA/TIA RS-232C)
  • Supported RS-232 signals: TxD, RxD, RTS, CTS, DSR, DCD, DTR, RxClk, TXclk, ExtClk, TST
  • RS-422/RS-485 interface (optional on LLM-336FXS)

Supported DTE data rates 

  • Asynchronous: 300, 600, 1200, 2400, 4800, 7200, 9600, 14k4, 19k2, 38k4, 57k6, 115k2 bit/s
    Asynchronous data formats: 10 and 11 bits: Formats: 8-N-1, 7-E-1, 7-O-1, 8-E-1, 8-O-1
  • Synchronous: 1200, 2400, 4800, 7k2, 9k6, 12k, 14k4, 16k8, 19k2, 21k6, 26k4, 28k8, 33k6 bit/s
    Clock sources: internal, external or slaved to receiver.

Line connection

  • 2-wire or 4-wire at RJ-11 connector
  • Normal impedance 600 Ω
  • High impedance 5 kΩ
  • RTS controlled TX impedance for multi-point operation
  • Transmit level: -8 to -30 dBm into  600 Ω (factory-pre set value: -11dBm)
  • Receiver input level range: -8..-43dBm
  • Receive thresholds:
  • -43 dBm on / -48 dBm off.
    -33 dBm on / -38 dBm off.
    -26 dBm on / -31dBm off.
    -16 dBm on / -21dBm off.


  • LLM-336FXD: Compact plastic housing
  • LLM-336FXR: 3HE, 5TE Rack card 
  • LLM-336FXS: Rugged steel housing (mounting flanges optional) 

Dimensions and weight

  •   LLM-336FXD: 95x145x30 mm LxWxH,  Weight: 210 gr.
  •   LLM-336FXR: 100x160 mm. Panel size: 3U (3HE) 5HP (5TE)
  •   LLM-336FXS: 250x130x30 mm LxWxH,  Weight: 970 gr. 

Power Supply and environmental

  • Power supply, Voltage ranges: 
  • - "VR1" versions: 9..36 Vdc (19..26Vac) (2.2 Watts) 
    - "VR2" versions: 18..72Vdc (22..50Vac) (2.2 Watts)
    - mains power adapter optional.

  • Temperature range:
  •  -25..+70C, Humidity: 5..95%  


  • CE mark: 89/336/CEE, 72/23/CEE, EN55022, EN50082-2, EN60950
  • IEC 61000-4-3, IEC 61000-4-4, IEC 61000-4-5, IEC 61000-4-6, IEC 61000-4-8, IEC 61000-4-9
  • Leased line operation: TBR15, TBR17
  • Climate: EN50125-3
  • Vibration: EN50125-3
MuLogic b.v. - Olivier van Noortstraat 4 - 3124LA - Schiedam - The Netherlands - Tel: +31 10 4700077 Fax: +31 10 4700958
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