Extend Two 4 Wire Voice Frequency Signals Over Fiber Optic Cable

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  • Rugged design, operating temperature range -40°C ~ 70°C
  • Transports voice frequency data 300Hz to 3,400Hz
  • Multiplexes 2 Independent 4 Wire Data Circuits over fiber
  • Supports 600 Ohm audio standard impedance
  • Single fiber and dual fiber transceivers available
  • Extend the signals long distances, up to 120km over fiber
  • Supports E&M signaling
  • Built-in alarm relay to indicate system health
  • Includes both DIN clip and wall mount ears for easy installation
  • System power range options: 24-48VDC or 125 VDC
  • Limited Lifetime Warranty

  • Made in USA

This industrial fiber optic media converter is designed to extend two 4 Wire Voice Frequency Signals over fiber optic cable. By extending 4 Wire signals over fiber cable you gain the advantage of sending the signal long distances, up to 120km, as well as gain noise immunity to RF and Electromagnetic Interference.

This system transports two circuits of 4 Wire Data and supports E&M signaling. The devices can be ordered with dual fiber or single fiber transceivers. The 4 wire data supports constant transmission of voice frequency ranging from 300Hz-3,400Hz which is suitable for a wide range of radio and SCADA applications. This RLH Fiber Link system is designed and made in the U.S.A. and covered by our Limited Lifetime Warranty.


For a comprehensive review of the product specs, please see the Data Sheet, or feel free to contact us with any questions.

Powering Voltage:
Standard Model - 24-48VDC
-A Model - 125VDC

Power Consumption:
6 Watts (Maximum)

Fiber Connectors:
ST or SC

Fiber Type:
Singlemode up to 120km
Multimode up to 2km, supports 62.5μm and 50μm

Analog Bandwidth (Voice Frequency):
300Hz to 3,400Hz

Channel Noise:
< 20dBrnC (15dBrnC typical)

Nominal Impedance:
600 Ohm input and output

Insertion Loss:
0dB +/- 0.5dB each direction

Overload Level:
8dBm into 600 Ohms

E&M Input:
24-48VDC, 3000Vrms optically isolated

E&M Output:
1500VRMS isolation by normally open solid state relay
Closed resistance 35 Ohms (220VAC or 330VDC @ 150mA max.) Open resistance >1M Ohms

Response Time:
Input to output 15-18ms

System Alarm Output:
Normally Closed / Normally Open (NCNO) Relay

Surge Protection:
Varistors & Automatic resettable fuses
DC Input Isolation 1.5kV

Powder coated steel and aluminum alloy
Physical Dimensions H 4.93” x W 1.20” x D 3.93” (125mm x 31mm x 100mm)

Mounting Style:
Standard DIN rail (T-35)
Wall mount (with included ears)

Temperature -40°F to +158°F (-40°C to +70°C)
Humidity 95%
MTBF 175,000 Hrs. (Circuit Board level)

Limited Lifetime

RLH 4 Wire Data with E&M Application

RLH 4 Wire Data with E&M Application

RJ-45 Pin Outs

RJ-45 Pin Outs

E&M Circuit

E&M Circuit


Download the RLH Data Sheet

Download the RLH User Guide

  • A complete system requires 2 units
  • Add -A for 125 VDC Powering Option

Please submit a quote request or contact your RLH sales representative for pricing and delivery information.